In CdSb + 3 % MnSb composite, structural properties have been studied, specific resistance ρ and Hall coefficient RH are measured at a high hydrostatic pressure of up to P ≤ 9 GPa. An irreversible structural phase transition is found at barometric dependencies p(P) and RH(P). From our experimental data, barometric dependencies of carrier concentration and their mobility are calculated. On the basis of the heterophase structure – effective medium model, characteristic points and parameters of the phase transition, and also dynamics of variation of the initial phase volume C1 as a function of pressure are computed. The latter dependence is in agreement with the investigation results of Raman scattering before and after application of pressure

Abakumov, P.V.

Arslanov, R.K.

Dobromyslov, M.B.

Dzhamamedov, R.G.

Kochura, A.V.

Marenkin, S.F.

Mollayev, A.Ju.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 7 No 4, 04088(4pp) (2015) Том 7 № 4, 04088(4cc) (2015)   2077-6772/2015/7(4)04088(4) 04088-1  2015 Sumy State University Structural Phase Transition in CdSb + 3 % MnSb Composite at a High Hydrostatic Pressure  R.G. Dzhamamedov1, A.Ju. Mollayev1,*, A.V. Kochura2, P.V. Abakumov2, R.K. Arslanov1,  S.F. Marenkin3,4, M.B. Dobromyslov5  1 Amirkhanov Institute of Physics, Dagestan Scientific Center, Russian Academy of Sciences,  94, Yaragskogo St., 367003 Makhachkala, Dagestan, Russia 2 South-West State University, Regional Centre of Nanotechnology,  94, 50 let Octyabrya St., 305040 Kursk, Russia  3 Institute of General and Inorganic Chemistry of Russian Academy of Sciences,  31, Leninskii Pr., 119991 Moscow, Russia 4 Moscow Institute of Steel and Alloys (National University of Science and Technology),  4, Leninskii Pr., 119049 Moscow, Russia 5 Pacific National University, 136, Tikhookeanskaya St., 680035 Khabarovsk, Russia  (Received 02 October 2015; published online 24 December 2015)  In CdSb + 3 % MnSb composite, structural properties have been studied, specific resistance  and Hall co-efficient RH are measured at a high hydrostatic pressure of up to P ≤ 9 GPa. An irreversible structural phase transition is found at barometric dependencies p(P) and RH(P). From our experimental data, barometric de-pendencies of carrier concentration and their mobility are calculated. On the basis of the heterophase struc-ture – effective medium model, characteristic points and parameters of the phase transition, and also dynam-ics of variation of the initial phase volume C1 as a function of pressure are computed. The latter dependence is in agreement with the investigation results of Raman scattering before and after application of pressure.  Keywords: Magnetic composite, Cadmium antimonide, Spintronic materials, Hydrostatic pressure, Transport properties   PACS numbers: 81.40.Rs, 81.40.Vw, 75.50.Pp, 78.30.Hv                                                             * a.mollaev@mail.ru 1. INTRODUCTION  Semiconducting compounds doped with 3d-metalls are the promising materials for magnetoelectronics (spintronics) [1]. Depending on the doping element, its atoms can both replace the cation vacancies in a base semiconductor and form interstitial defects. In this case, the state of a diluted magnetic semiconductor is imple-mented. However, if the limit of solubility is surpassed, phase layering in the lattice of a base semiconductor may occur, which results in the formation of micro- or nanoscale magnetic inclusions (clusters). Diluted mag-netic semiconductor In1 – хMnxSb with nanoscale inclu-sions of ferromagnetic semimetal MnSb with Courier temperature of around 600 K [2] is an example when both cases given above are realized. A similar situation occurs for semiconductors of the group AIIBV, where B  Sb, doped with manganese. The present work con-tinues that research [5-8] at high hydrostatic pressures up to 9 GPa. Earlier, in works [7, 8], undoped single crystal sam-ples p-CdSb were studied. The samples were oriented along crystallographic directions [001] (sample No 1) and [010] (sample No 2). Specific electrical resistance ρ and Hall coefficient RH was measured at high hydrostatic pressure P  7 GPa at elevation and drop off of pressure within the range of room temperatures. At dependencies (P) and RH(P), structural phase transitions were found. In sample No 1, a reversible semiconductor-semiconductor phase transition was observed and in sample No 2 an irreversible phase transition accompa-nied by the matter decomposition occurred. X-ray study of the samples after loading has shown that the de-formed sample No 1 oriented along [001] produced at Laue pattern continuous rings with sharp maxima – polycrystal with texture. For sample №2, the swing curve consisted from a number of peaks that correspond-ed to the reflection off individual blocks. Relative disori-entation of these blocks was ~ 1-1.50, indicating consid-erable impairment of the sample quality. We have investigated structural and electrical prop-erties of composite sample CdSb + 3 % MnSb at a high hydrostatic pressure of up to 9 GPa in the range of room temperature.  2. EXPERIMANTAL DETAILS  Original crystals were prepared with directional crystallization according to Bridgeman from polycrystal CdSb + 3 % MnSb ingots, which were produced before-hand by alloying of antimonides cadmium and manga-nese. The samples were cut from the central part of the crystal and then underwent chemical-mechanical polish-ing with abrasive particles whose size was not greater than 20 nm. To examine the sample structure, the composition and element distribution at the surface, scanning elec-tron microscope (SEM) JSM-6610LV (Jeol) with attach-ment for energy dispersive X-ray spectroscopy (EDXS) X-MaxN (Oxford Instruments) was used. Spectra of Raman scattering (RS) were measured at room temperature with the use of combined system with confocal fluores-cent spectrometer and RS spectrometer OmegaScopeTM (AIST-NT Inc.) featuring laser wavelength of 532 nm,  G. DZHAMAMEDOV, A.JU. MOLLAYEV, ET AL. J. NANO- ELECTRON. PHYS. 7, 04088 (2015)   04088-2 power of 50 mW. The spot of a focused light at the sam-ple surface was around 500 nm in diameter. The spectral resolution was 0.8 cm – 1. The installation for measuring kinetic coefficients at hydrostatic pressures P  9 GPa was a high- pres-sure device such as toroid [9], which was upgraded to concurrently measure several kinetic coefficients. In order to concurrently measure specific resistance and Hall effect a many-turn solenoid [10] was used, which made it possible to produce a magnetic field H  5 kOe. A fluoroplastic capsule with a volume of  80 mm3 was applied as a working cell, which had 12 electric inputs. That made it possible to measure specific resistance, Hall effect, and control pressure at compression and decompression. A manganin manome-ter was calibrated by using fixed points (Bi, Tl, etc.) Samples were prepared as parallelepipeds with sizes of 2.8  0.7  0.5 mm. As a medium transferring pressure, a mixture of methanol and ethanol (4 : 1) hydrostatic up to 10 GPa was used [11]. To determine to what ex-tent the medium was hydrostatic, two identical single-crystal samples n-Ge with   1.75 Ω∙cm were put in a measuring cell perpendicular to each other. The quan-tity  was measured as a function of pressure up to 9 GPa at 300 K. Both samples revealed that at a fixed pressure the values of specific resistance did not coin-cide when the pressure was elevated and lowered. This fact indicates that there were not axis strengths that had been observed earlier in the range 4-5 GPa when as a transfer medium n-penthane-isoamyl alcohol was used. In addition to that, these data about dependence R(P) corroborate that the pressure was  rather hydro-static and  shear stresses were absent. Contacts for measuring electrical properties were made by soldering with solders at the basis of tin. The error in measuring resistance, Hall effect and pressure was not greater than  3 %, 3.5 % and 3 %, respectively.  3. RESULTS AND DISCUSSION  Typical images of the sample surface obtained with SEM are given in Fig. 1. Clearly seen are defects of the sample structure as cracks and volume inclusions with a nonhomogeneous distribution. These inclusions are both of point and needle-like shape with the smallest side of 0.5-1 m. EDXS has revealed that the areas without defects con-sisted only of Cd and Sb atoms in virtually equal pro-portions. Within the area of inclusions in EDXS spec-tra, peaks were appeared corresponding to Mn atoms. Distribution maps of Cd, Sb, Mn in the area with inclusions (Fig. 2) measured with EDXS demonstrate the excessive content of Mn in the areas where there are fewer Cd atoms. In doing so, the distribution of Sb atoms is more uniform with a little more content in the areas where many Mn atoms occur. Therefore, inclu-sions most likely present the phase of MnSb1 +  (  0), as it was found earlier in eutectic compositions InSb-MnSb [12]. It should be noted that MnSb1 +  is a ferro-magnetic semimetal with the highest Courier tempera-ture (TC) among compounds Mn-V that reaches 585 K for MnSb [13]. In this case, a decrease in Sb content (  0) results in a decrease in TC [14], whereas at   0 TC does not change [12].   Fig. 1 – SEM image of the sample surface for CdSb + 3 % MnSb      Fig. 2 – Element distribution at the fraction of the sample surface for CdSb + 3 % MnSb having inclusions. Image for Sb content is provided after graphical processing in order to com-pare areas where the content of Sb is little excessive, big Mn content and the absence of Cd  The samples under investigation, therefore, should most likely have ferromagnetic properties with TC  585 К. Crystal lattice of CdSb belongs to the orthorhombic system (spatial group Pbca) and has 16 atoms in the elementary cell. In  point of the Brillouin zone, 48 normal vibration modes stand out [15]:   Г  6(Ag + B1g + B2g + B3g + Au + B1u + B2u + B3u)   of which 24 are RS-active. Earlier, at experimental study of RS-spectra for single crystals CdSb, 22 modes were found: Ag (37.5, 53, 61, 82, 107 and 173 cm – 1); B1g (53, 66 and 178 cm – 1); B2g (53, 107 and 179 cm – 1) and B3g (49, 61, 70, 128, 154 and 171 cm – 1) [16].  Raman spectra of CdSb + 3 % MnSb sample before application of 8 GPa pressure and after that are shown in Fig.3. Because of features of the experimental device, one was able to measure them only at   100 cm – 1. In this region, one can see a number of phonon modes of CdSb with a small increase in their frequency (not more  STRUCTURAL PHASE TRANSITION IN CDSB + 3 % MNSB COMPOSITE… J. NANO- ELECTRON. PHYS. 7, 04088 (2015)   04088-3 than 1-2 cm – 1) compared to the values given above for an undoped single crystal. This fact is in agreement with the results of [17] where such frequency change of phonons was explained by the replacement of Cd atoms with lighter Zn atoms. For CdSb + 3 % MnSb sample, the situation is most likely similar and part of Mn at-oms replaces Cd atoms, forming this way solid solution of CdxMn1 – xSb. At Raman spectra of the sample before and after pressure application identical modes are ob-served. However, the spectrum intensity after pressure application is reduced; oscillator strength changes and a broad weak maximum appears around 200 cm – 1. Thus, the sample crystallinity was likely lowered and it went a partial phase layering. There was irreversible phase transition, which is indicated by the fact that after pressure application the Raman spectrum ampli-tude is decreased.    Fig. 3 – Raman spectra for CdSb + 3 % MnSb sample:  #1 – before 8GPa pressure application; #2 – after application. Arrows indicate phonon modes observed at both spectra  Experimental barometric dependencies of specific resistance  and the Hall coefficient RH are given in Fig. 4a. Barometric dependencies of carrier concentra-tions p(P) and mobility (P) at room temperatures cal-culated with consideration for  and RH  for the compo-site CdSb + 3 % MnSb are depicted in Fig. 4b. It is seen from Fig. 4a that specific resistance is almost constant up to pressure P ≈ 1.2 GPa and then increases three-fold. At a pressure about 2 GPa, resistance reaches its maximum and then begins to decrease with various barometric coefficients and turns lower by almost 2 orders of magnitude. In the saturation region, specific resistance equals  ≈ 7.4∙10 – 5 Ohm∙cm, i.e. metal conductivity oc-curs. Whereas at atmospheric pressure  ≈ 0,1 Ohm·cm, i.e. semiconductor-to-metal phase transition takes place. At depressurization, specific resistance at P ≈ 1 GPa is virtually constant but then increases. Initial values of resistance before and after load application are not the same, which is indicative of the fact that irreversi-ble structural phase transition occurred accompanied by the partial layering of phases. At depressurization, hysteresis is observed, which is typical for first -order phase transitions.    Fig. 4 – Barometric dependencies: a) of reduced to atmospher-ic pressure specific resistance and Hall coefficient (black sym-bols – increase in pressure, open – depressurization); b) con-centration (open symbols) and mobility (black symbols) at pressure elevation  Hall coefficient (Fig. 4a) varies weakly to a pressure P ≈ 2 GPa and then sharply decreases by more than two orders of magnitude and at P ≈ 6,7 GPa reaches saturation. At depressurization, hysteresis is also ob-served. In the saturation region, the carrier concentration  ≈ 7.5∙1020 cm – 3, which is characteristic of metals. The values of Hall coefficient before and after pressure ap-plication do not coincide, which supports the conclusion that in p-CdSb + 3 % MnSb irreversible semiconductor-to-metal phase transition occurred. At depressuriza-tion, hysteresis is observed. Fig. 4b shows barometric dependencies of concen-tration p(P) and mobility (P) at room temperatures. It is seen from Fig. 5 that at atmospheric pressure p ≈ 3.7∙1018 cm – 1 and up to pressures P ≈ 1.4 GPa is nearly constant. Then with pressure increasing, p also increases and at P  7 GPa reaches saturation. In the saturation region p  7.5∙1020 сm – 1, which once again supports the conclusion about phase transition being semiconductor-metal. The mobility value  that at atmospheric pressure is equal to 17.3 cm2/V·s decreases with pressure in-creasing and in the minimum at P  4.2 GPa equals 1 cm2/V·s, i.e. becomes lower by 17-fold. Then mobility increases again and at P  7 GPa becomes greater by 2 orders of magnitude and reaches saturation. By using experimental values of the origin Рb and the end of the phase transition Рe, at pressure elevation and depressurization Pb, Pe according to the ideas giv-en in [18-23] and the procedure proposed in [20] some characteristic points and phase transformation param-eters at high pressure have been calculated.  Table 1 – Parameters characterizing phase transition at high pressures in p-CdSb + MnSb (3 % Mn)   Pb, GPa Pe,  GPa Pо,  GPa Pоm  GPa Ph.f.  GPa Pb,  GPa Pe,  GPa Pо,  GPa Pоm  GPa Ph.f. GPa Ph.t GPa 2.9 7.2 1.9 5.0 4.3 0.9 0.1 3.6 0.5 0.8 4.5  G. DZHAMAMEDOV, A.JU. MOLLAYEV, ET AL. J. NANO- ELECTRON. PHYS. 7, 04088 (2015)   04088-4   Fig. 5 – Volume fraction of the initial phase C1 as a function of pressure at compression and decompression for  р-CdSb + MnSb (3 % Mn)  From the model heterophase structure – effective medium [19], we have calculated dynamics of changes in the volume fraction of the initial phase C1 versus pressure. At PH – C1  1 and С2  0 and at PK – C1  0 and С2  1. Here С1 and С2 are relative volumes of phases C1  V1/(V1 + V2), C2  V2/(V1 + V2), C1 + C2  1, where V1  is the initial phase volume, V2 is the volume of the produced phase. Depicted in Fig. 5 is the de-pendence of the volume fraction of the initial phase C1(P) on the pressure at its elevation and depressuriza-tion for the sample p-CdSb + 3 % MnSb. It should be noted that the ratio of C1 before the cycle of pressure application and after is in qualitative agreement with the ratio of Raman spectra intensities (Fig. 3). After pressure application, both the values of C1 and spec-trum intensity decrease.  4. CONCLUSION  Measurements of structural features, Raman spec-tra, Hall’s coefficient and specific resistance at pressure elevation and depressurization at room temperatures in p-CdSb + 3 % MnSb composite have revealed an ir-reversible structural phase transition. Barometric de-pendencies of mobility and carrier concentration have been calculated. From the model heterophase struc-ture- effective medium, characteristic points and pa-rameters of phase transition, and also the volume of the initial phase C1 as a function of pressure have been computed. The reported study was funded in part by RFBR ac-cording to the research project No 13-02-01105-а.   REFERENCES  1. V.A. Ivanov, T.G. Aminov, V.M. Novotortsev, V.T. Kalinnikov, Russ. Chem. Bull. 53, 2357 (2004). 2. A.V. Kochura B. Aronzon, K.G. Lisunov, A.V. Lashkul, A. Sidorenko, R. De Renzi, S.F. Marenkin, M. Alam, A.P. Kuzmenko, E. Lahderanta, J. Appl. Phys. 113, 083905 (2013). 3. S.F. Marenkin, V.M. Trukhan, I.V. Fedorchenko, T.V. Shoulkavaya, Russ. J. Inorg. Chem. 59, 355 (2014). 4. A.V. Kochura, S.F. Marenkin, A.D. Izotov, P.N. Vasilev, P.V. Abakumov, A.P. Kuzmenko, Inorg. Mater. 51, 754 (2015). 5. A.Yu. Mollaev, Fizika i Tehnika Visokikh Davlenii 14, 34 (2004). 6. A.Yu. Mollaev, L.A. Saipulaeva, R.K. Arslanov, A.N. Babushkin, Inorg. Mater. 50, 861 (2014). 7. A.Yu. Mollaev, R.K. Arslanov, R.G. Dzhamamedov, S.F. Marenkin, S.A. Varnavskii, Inorg. Mater. 41, 217 (2005). 8. A.Yu. Mollaev, R.K. Arslanov, R.G. Dzhamamedov, S.F. Marenkin, S.A. Varnavskii, Fizika i Tehnika Visokikh Davlenii 14, 132 (2004). 9. L.G. Khvostantsev, L.P. Vereshagin, A.P. Novikov, High Temp. High Pressure 9, 637 (1977). 10. A.Yu. Mollaev, L.A. Saipulaeva, R.K. Arslanov, S.F. Marenkin, Inorg. Mater. 37, 327 (2001). 11. G.J. Piermarini, S. Block, J.D. Barnett, J. Appl. Phys. 44, 5377 (1973). 12. V.M. Novotortsev, A.V. Kochura, S.F. Marenkin, I.V. Fedorchenko, S.V. Drogunov, A. Lashkul, E. Lahderanta, Russ. J. Inorg. Chem. 56, 1951 (2011). 13. W.J. Takei, D.E. Cox, G. Shirane, Phys. Rev. 129, 2008 (1963). 14. I. Teramoto, A.M.J.G. Van Run, J. Phys. Chem. Solids 29, 347 (1968). 15. D. Houde, J. Lefaivre, S. Jandl, E. Arushanov, Sol. St. Comm. 41, 325 (1982). 16. D.M. Triches, S.M. Souza, J.C. de Lima, T.A. Grandi, C.E.M. Campos, A. Polian, J.P. Ltie, F. Baudelet, J.C. Chervin. J. Appl. Phys. 106, 013509 (2009). 17. D.V. Smirnov, D.V. Mashovets, S. Pasquier, J. Leotin, P. Puech, G. Landa, Yu.V. Roznovan, Semicond. Sci. Technol. 9, 333 (1994). 18. A.L. Roitburd, Phys.-Usp. 17, 326 (1974). 19. A.L. Roitburd, Phys. Solid State 25, 33 (1983). 20. A.Yu. Mollaev, R.K. Arslanov, R.I. Akhmedov, L.A. Saipulaeva, Fizika i Tehnika Visokikh Davlenii 4, 66 (1994). 21. A.L. Roitburd, Phys. Solid State 26, 2025 (1984). 22. V.N. Kozlov, G.R. Umarov, A.A. Firsov, Fizika i Tehnika Visokikh Davlenii 23, 9 (1986). 23. M.I. Daunov, A.B. Magomedov, A.Yu. Mollaev, S.M. Salikhov, L.A. Saipulaeva, Sverkhtverdye Materialy 3, 3 (1992).  

Structural Phase Transition in CdSb + 3 % MnSb Composite at a High Hydrostatic Pressure

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 4, 04088(4pp) (2015) Том 7 № 4, 04088(4cc) (2015) 
 
 
2077-6772/2015/7(4)04088(4) 04088-1  2015 Sumy State University 
Structural Phase Transition in CdSb + 3 % MnSb Composite at a High Hydrostatic Pressure 
 
R.G. Dzhamamedov1, A.Ju. Mollayev1,*, A.V. Kochura2, P.V. Abakumov2, R.K. Arslanov1,  
S.F. Marenkin3,4, M.B. Dobromyslov5 
 
1 Amirkhanov Institute of Physics, Dagestan Scientific Center, Russian Academy of Sciences,  
94, Yaragskogo St., 367003 Makhachkala, Dagestan, Russia 
2 South-West State University, Regional Centre of Nanotechnology,  
94, 50 let Octyabrya St., 305040 Kursk, Russia  
3 Institute of General and Inorganic Chemistry of Russian Academy of Sciences,  
31, Leninskii Pr., 119991 Moscow, Russia 
4 Moscow Institute of Steel and Alloys (National University of Science and Technology),  
4, Leninskii Pr., 119049 Moscow, Russia 
5 Pacific National University, 136, Tikhookeanskaya St., 680035 Khabarovsk, Russia 
 
(Received 02 October 2015; published online 24 December 2015) 
 
In CdSb + 3 % MnSb composite, structural properties have been studied, specific resistance  and Hall co-
efficient RH are measured at a high hydrostatic pressure of up to P ≤ 9 GPa. An irreversible structural phase 
transition is found at barometric dependencies p(P) and RH(P). From our experimental data, barometric de-
pendencies of carrier concentration and their mobility are calculated. On the basis of the heterophase struc-
ture – effective medium model, characteristic points and parameters of the phase transition, and also dynam-
ics of variation of the initial phase volume C1 as a function of pressure are computed. The latter dependence is 
in agreement with the investigation results of Raman scattering before and after application of pressure. 
 
Keywords: Magnetic composite, Cadmium antimonide, Spintronic materials, Hydrostatic pressure, 
Transport properties 
 
 PACS numbers: 81.40.Rs, 81.40.Vw, 75.50.Pp, 
78.30.Hv 
 
 
                                                          
* a.mollaev@mail.ru 
1. INTRODUCTION 
 
Semiconducting compounds doped with 3d-metalls 
are the promising materials for magnetoelectronics 
(spintronics) [1]. Depending on the doping element, its 
atoms can both replace the cation vacancies in a base 
semiconductor and form interstitial defects. In this case, 
the state of a diluted magnetic semiconductor is imple-
mented. However, if the limit of solubility is surpassed, 
phase layering in the lattice of a base semiconductor 
may occur, which results in the formation of micro- or 
nanoscale magnetic inclusions (clusters). Diluted mag-
netic semiconductor In1 – хMnxSb with nanoscale inclu-
sions of ferromagnetic semimetal MnSb with Courier 
temperature of around 600 K [2] is an example when 
both cases given above are realized. A similar situation 
occurs for semiconductors of the group AIIBV, where 
B  Sb, doped with manganese. The present work con-
tinues that research [5-8] at high hydrostatic pressures 
up to 9 GPa. 
Earlier, in works [7, 8], undoped single crystal sam-
ples p-CdSb were studied. The samples were oriented 
along crystallographic directions [001] (sample No 1) and 
[010] (sample No 2). Specific electrical resistance ρ and 
Hall coefficient RH was measured at high hydrostatic 
pressure P  7 GPa at elevation and drop off of pressure 
within the range of room temperatures. At dependencies 
(P) and RH(P), structural phase transitions were found. 
In sample No 1, a reversible semiconductor-
semiconductor phase transition was observed and in 
sample No 2 an irreversible phase transition accompa-
nied by the matter decomposition occurred. X-ray study 
of the samples after loading has shown that the de-
formed sample No 1 oriented along [001] produced at 
Laue pattern continuous rings with sharp maxima – 
polycrystal with texture. For sample №2, the swing 
curve consisted from a number of peaks that correspond-
ed to the reflection off individual blocks. Relative disori-
entation of these blocks was ~ 1-1.50, indicating consid-
erable impairment of the sample quality. 
We have investigated structural and electrical prop-
erties of composite sample CdSb + 3 % MnSb at a high 
hydrostatic pressure of up to 9 GPa in the range of room 
temperature. 
 
2. EXPERIMANTAL DETAILS 
 
Original crystals were prepared with directional 
crystallization according to Bridgeman from polycrystal 
CdSb + 3 % MnSb ingots, which were produced before-
hand by alloying of antimonides cadmium and manga-
nese. The samples were cut from the central part of the 
crystal and then underwent chemical-mechanical polish-
ing with abrasive particles whose size was not greater 
than 20 nm. 
To examine the sample structure, the composition 
and element distribution at the surface, scanning elec-
tron microscope (SEM) JSM-6610LV (Jeol) with attach-
ment for energy dispersive X-ray spectroscopy (EDXS) X-
MaxN (Oxford Instruments) was used. Spectra of Raman 
scattering (RS) were measured at room temperature 
with the use of combined system with confocal fluores-
cent spectrometer and RS spectrometer OmegaScopeTM 
(AIST-NT Inc.) featuring laser wavelength of 532 nm, 
 G. DZHAMAMEDOV, A.JU. MOLLAYEV, ET AL. J. NANO- ELECTRON. PHYS. 7, 04088 (2015) 
 
 
04088-2 
power of 50 mW. The spot of a focused light at the sam-
ple surface was around 500 nm in diameter. The spectral 
resolution was 0.8 cm – 1. 
The installation for measuring kinetic coefficients 
at hydrostatic pressures P  9 GPa was a high- pres-
sure device such as toroid [9], which was upgraded to 
concurrently measure several kinetic coefficients. 
In order to concurrently measure specific resistance 
and Hall effect a many-turn solenoid [10] was used, 
which made it possible to produce a magnetic field 
H  5 kOe. A fluoroplastic capsule with a volume of 
 80 mm3 was applied as a working cell, which had 
12 electric inputs. That made it possible to measure 
specific resistance, Hall effect, and control pressure at 
compression and decompression. A manganin manome-
ter was calibrated by using fixed points (Bi, Tl, etc.) 
Samples were prepared as parallelepipeds with sizes of 
2.8  0.7  0.5 mm. As a medium transferring pressure, 
a mixture of methanol and ethanol (4 : 1) hydrostatic 
up to 10 GPa was used [11]. To determine to what ex-
tent the medium was hydrostatic, two identical single-
crystal samples n-Ge with   1.75 Ω∙cm were put in a 
measuring cell perpendicular to each other. The quan-
tity  was measured as a function of pressure up to 
9 GPa at 300 K. Both samples revealed that at a fixed 
pressure the values of specific resistance did not coin-
cide when the pressure was elevated and lowered. This 
fact indicates that there were not axis strengths that 
had been observed earlier in the range 4-5 GPa when 
as a transfer medium n-penthane-isoamyl alcohol was 
used. In addition to that, these data about dependence 
R(P) corroborate that the pressure was  rather hydro-
static and  shear stresses were absent. 
Contacts for measuring electrical properties were 
made by soldering with solders at the basis of tin. The 
error in measuring resistance, Hall effect and pressure 
was not greater than  3 %, 3.5 % and 3 %, respectively. 
 
3. RESULTS AND DISCUSSION 
 
Typical images of the sample surface obtained with 
SEM are given in Fig. 1. 
Clearly seen are defects of the sample structure as 
cracks and volume inclusions with a nonhomogeneous 
distribution. These inclusions are both of point and 
needle-like shape with the smallest side of 0.5-1 m. 
EDXS has revealed that the areas without defects con-
sisted only of Cd and Sb atoms in virtually equal pro-
portions. Within the area of inclusions in EDXS spec-
tra, peaks were appeared corresponding to Mn atoms. 
Distribution maps of Cd, Sb, Mn in the area with 
inclusions (Fig. 2) measured with EDXS demonstrate 
the excessive content of Mn in the areas where there 
are fewer Cd atoms. In doing so, the distribution of Sb 
atoms is more uniform with a little more content in the 
areas where many Mn atoms occur. Therefore, inclu-
sions most likely present the phase of MnSb1 +  (  0), 
as it was found earlier in eutectic compositions InSb-
MnSb [12]. It should be noted that MnSb1 +  is a ferro-
magnetic semimetal with the highest Courier tempera-
ture (TC) among compounds Mn-V that reaches 585 K 
for MnSb [13]. In this case, a decrease in Sb content 
(  0) results in a decrease in TC [14], whereas at   0 
TC does not change [12]. 
 
 
Fig. 1 – SEM image of the sample surface for CdSb + 3 % MnSb 
 
  
 
 
Fig. 2 – Element distribution at the fraction of the sample 
surface for CdSb + 3 % MnSb having inclusions. Image for Sb 
content is provided after graphical processing in order to com-
pare areas where the content of Sb is little excessive, big Mn 
content and the absence of Cd 
 
The samples under investigation, therefore, should 
most likely have ferromagnetic properties with 
TC  585 К. 
Crystal lattice of CdSb belongs to the orthorhombic 
system (spatial group Pbca) and has 16 atoms in the 
elementary cell. In  point of the Brillouin zone, 
48 normal vibration modes stand out [15]:  
 
Г  6(Ag + B1g + B2g + B3g + Au + B1u + B2u + B3u)  
 
of which 24 are RS-active. Earlier, at experimental 
study of RS-spectra for single crystals CdSb, 22 modes 
were found: Ag (37.5, 53, 61, 82, 107 and 173 cm – 1); 
B1g (53, 66 and 178 cm – 1); B2g (53, 107 and 179 cm – 1) 
and B3g (49, 61, 70, 128, 154 and 171 cm – 1) [16].  
Raman spectra of CdSb + 3 % MnSb sample before 
application of 8 GPa pressure and after that are shown 
in Fig.3. Because of features of the experimental device, 
one was able to measure them only at   100 cm – 1. In 
this region, one can see a number of phonon modes of 
CdSb with a small increase in their frequency (not more 
 STRUCTURAL PHASE TRANSITION IN CDSB + 3 % MNSB COMPOSITE… J. NANO- ELECTRON. PHYS. 7, 04088 (2015) 
 
 
04088-3 
than 1-2 cm – 1) compared to the values given above for 
an undoped single crystal. This fact is in agreement 
with the results of [17] where such frequency change of 
phonons was explained by the replacement of Cd atoms 
with lighter Zn atoms. For CdSb + 3 % MnSb sample, 
the situation is most likely similar and part of Mn at-
oms replaces Cd atoms, forming this way solid solution 
of CdxMn1 – xSb. At Raman spectra of the sample before 
and after pressure application identical modes are ob-
served. However, the spectrum intensity after pressure 
application is reduced; oscillator strength changes and 
a broad weak maximum appears around 200 cm – 1. 
Thus, the sample crystallinity was likely lowered and it 
went a partial phase layering. There was irreversible 
phase transition, which is indicated by the fact that 
after pressure application the Raman spectrum ampli-
tude is decreased. 
 
 
 
Fig. 3 – Raman spectra for CdSb + 3 % MnSb sample:  
#1 – before 8GPa pressure application; #2 – after application. 
Arrows indicate phonon modes observed at both spectra 
 
Experimental barometric dependencies of specific 
resistance  and the Hall coefficient RH are given in 
Fig. 4a. Barometric dependencies of carrier concentra-
tions p(P) and mobility (P) at room temperatures cal-
culated with consideration for  and RH  for the compo-
site CdSb + 3 % MnSb are depicted in Fig. 4b. 
It is seen from Fig. 4a that specific resistance is almost 
constant up to pressure P ≈ 1.2 GPa and then increases 
three-fold. At a pressure about 2 GPa, resistance reaches 
its maximum and then begins to decrease with various 
barometric coefficients and turns lower by almost 2 orders 
of magnitude. In the saturation region, specific resistance 
equals  ≈ 7.4∙10 – 5 Ohm∙cm, i.e. metal conductivity oc-
curs. Whereas at atmospheric pressure  ≈ 0,1 Ohm·cm, 
i.e. semiconductor-to-metal phase transition takes place. 
At depressurization, specific resistance at P ≈ 1 GPa 
is virtually constant but then increases. Initial values 
of resistance before and after load application are not 
the same, which is indicative of the fact that irreversi-
ble structural phase transition occurred accompanied 
by the partial layering of phases. At depressurization, 
hysteresis is observed, which is typical for first -order 
phase transitions. 
 
 
 
Fig. 4 – Barometric dependencies: a) of reduced to atmospher-
ic pressure specific resistance and Hall coefficient (black sym-
bols – increase in pressure, open – depressurization); b) con-
centration (open symbols) and mobility (black symbols) at 
pressure elevation 
 
Hall coefficient (Fig. 4a) varies weakly to a pressure 
P ≈ 2 GPa and then sharply decreases by more than 
two orders of magnitude and at P ≈ 6,7 GPa reaches 
saturation. At depressurization, hysteresis is also ob-
served. 
In the saturation region, the carrier concentration 
 ≈ 7.5∙1020 cm – 3, which is characteristic of metals. The 
values of Hall coefficient before and after pressure ap-
plication do not coincide, which supports the conclusion 
that in p-CdSb + 3 % MnSb irreversible semiconductor-
to-metal phase transition occurred. At depressuriza-
tion, hysteresis is observed. 
Fig. 4b shows barometric dependencies of concen-
tration p(P) and mobility (P) at room temperatures. It 
is seen from Fig. 5 that at atmospheric pressure 
p ≈ 3.7∙1018 cm – 1 and up to pressures P ≈ 1.4 GPa is 
nearly constant. Then with pressure increasing, p also 
increases and at P  7 GPa reaches saturation. In the 
saturation region p  7.5∙1020 сm – 1, which once again 
supports the conclusion about phase transition being 
semiconductor-metal. 
The mobility value  that at atmospheric pressure 
is equal to 17.3 cm2/V·s decreases with pressure in-
creasing and in the minimum at P  4.2 GPa equals 
1 cm2/V·s, i.e. becomes lower by 17-fold. Then mobility 
increases again and at P  7 GPa becomes greater by 2 
orders of magnitude and reaches saturation. 
By using experimental values of the origin Рb and 
the end of the phase transition Рe, at pressure elevation 
and depressurization Pb, Pe according to the ideas giv-
en in [18-23] and the procedure proposed in [20] some 
characteristic points and phase transformation param-
eters at high pressure have been calculated. 
 
Table 1 – Parameters characterizing phase transition at high 
pressures in p-CdSb + MnSb (3 % Mn) 
 
 
Pb, 
GPa 
Pe,  
GPa 
Pо,  
GPa 
Pоm  
GPa 
Ph.f.  
GPa 
Pb,  
GPa 
Pe,  
GPa 
Pо,  
GPa 
Pоm  
GPa 
Ph.f. 
GPa 
Ph.t 
GPa 
2.9 7.2 1.9 5.0 4.3 0.9 0.1 3.6 0.5 0.8 4.5 
 G. DZHAMAMEDOV, A.JU. MOLLAYEV, ET AL. J. NANO- ELECTRON. PHYS. 7, 04088 (2015) 
 
 
04088-4 
 
 
Fig. 5 – Volume fraction of the initial phase C1 as a function 
of pressure at compression and decompression for  
р-CdSb + MnSb (3 % Mn) 
 
From the model heterophase structure – effective 
medium [19], we have calculated dynamics of changes 
in the volume fraction of the initial phase C1 versus 
pressure. At PH – C1  1 and С2  0 and at PK – C1  0 
and С2  1. Here С1 and С2 are relative volumes of 
phases C1  V1/(V1 + V2), C2  V2/(V1 + V2), C1 + C2  1, 
where V1  is the initial phase volume, V2 is the volume 
of the produced phase. Depicted in Fig. 5 is the de-
pendence of the volume fraction of the initial phase 
C1(P) on the pressure at its elevation and depressuriza-
tion for the sample p-CdSb + 3 % MnSb. It should be 
noted that the ratio of C1 before the cycle of pressure 
application and after is in qualitative agreement with 
the ratio of Raman spectra intensities (Fig. 3). After 
pressure application, both the values of C1 and spec-
trum intensity decrease. 
 
4. CONCLUSION 
 
Measurements of structural features, Raman spec-
tra, Hall’s coefficient and specific resistance at pressure 
elevation and depressurization at room temperatures 
in p-CdSb + 3 % MnSb composite have revealed an ir-
reversible structural phase transition. Barometric de-
pendencies of mobility and carrier concentration have 
been calculated. From the model heterophase struc-
ture- effective medium, characteristic points and pa-
rameters of phase transition, and also the volume of 
the initial phase C1 as a function of pressure have been 
computed. 
The reported study was funded in part by RFBR ac-
cording to the research project No 13-02-01105-а. 
 
 
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Structural Phase Transition in CdSb + 3 % MnSb Composite at a High Hydrostatic Pressure

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