Magnetism and specific heat of TmRhX (X = Ga, Ge) compounds

Magnetic and specific heat data of the TmRhX (X = Ga, Ge) compounds are reported. These compounds crystallize in an orthorhombic crystal structure of the TiNiSi-type (space group Pnma). Magnetic data indicate that the compounds are antiferromagnets with the Néel temperature $T_{N}$ equal to 3.9 K for TmRhGa and 6.0 K for TmRhGe. Magnetic susceptibility of TmRhGe has an additional peak at $T_{t}$ = 10.6 K. In TmRhGe temperature dependence of χ"(T), the positions of both the peaks at $T_{N}$ and $T_{t}$ change with frequency indicating a relaxation process. These data suggest that with the decreasing temperature, first a cluster glass state and next the long-range aniferromagnetic order exists

Influence of carbon on spin reorientation processes in Er 2-xRxFe14C (R = Gd, Pr) - Mossbauer and magnetometric studies

The Er2¡xRxFe14C (R=Gd, Pr) polycrystalline compounds have been synthesized and investigated with 57Fe Mössbauer spectroscopy and magnetic measurements. The spin reorientation phenomena were studied extensively by narrow step temperature scanning in the neighborhood of the spin reorientation temperature. Obtained Mössbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mössbauer spectra were obtained, temperature and composition dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. Initial magnetization versus temperature measurements (in zero and non-zero external field) for Er2¡xGdxFe14C compounds allowed to establish the temperature regions of reorientation, change of magnetization value during the transition process. The results obtained with different methods were analyzed and the spin arrangement diagrams were constructed. Data obtained for Er2¡xGdxFe14C were compared with those for Er2¡xGdxFe14B series

Influence of carbon on spin reorientation processes in Er_{2-x}R_{x}Fe_{14}C (R = Gd, Pr) - Mössbauer and magnetometric studies

The $Er_{2-x}R_{x}Fe_{14}C$ (R=Gd, Pr) polycrystalline compounds have been synthesized and investigated with $\text{}^{57}Fe$ Mössbauer spectroscopy and magnetic measurements. The spin reorientation phenomena were studied extensively by narrow step temperature scanning in the neighborhood of the spin reorientation temperature. Obtained Mössbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mössbauer spectra were obtained, temperature and composition dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. Initial magnetization versus temperature measurements (in zero and non-zero external field) for $Er_{2-x}Gd_{x}Fe_{14}C$ compounds allowed to establish the temperature regions of reorientation, change of magnetization value during the transition process. The results obtained with different methods were analyzed and the spin arrangement diagrams were constructed. Data obtained for $Er_{2-x}Gd_{x}Fe_{14}C$ were compared with those for $Er_{2-x}Gd_{x}Fe_{14}B$ series

Martensitic transformation, magnetic entropy, and adiabatic temperature changes in bulk and ribbon Ni48Mn39.5Sn12.5−xInx (x = 2, 4, 6) metamagnetic shape memory alloys

Martensitic transformation, magnetic entropy, and direct adiabatic temperature changes in Ni48Mn39.5Sn12.5− xInx (x = 2, 4, 6) metamagnetic Heusler bulk and grain-constrained ribbon alloys were studied. All alloys showed a typical L21 structure in austenite and the 4O structure in martensite. Their relative volume contributions changed depending on In content. With increasing In concentration, the martensitic transformation temperature increased, whereas the Curie temperature of austenite decreased. The magnetic entropy change under magnetic field of 5 T attained maximum of 20 J/kgK in the bulk and 14.4 J/kgK in the ribbon alloys with the Ni48Mn39.5Sn8.5In4 nominal composition. The corresponding adiabatic temperature change under 1.7 T yielded 1.3 K for the Ni48Mn39.5Sn8.5In4 bulk alloy. Despite grain confinement, melt spinning was found to stabilize martensite phase. Changes observed were discussed with relation to strengthened covalency imposed by In substitution

Moessbauer spectroscopy evidence for the lack of iron magnetic moment in superconducting FeSe

Superconducting FeSe has been investigated by measurements of the magnetic susceptibility versus temperature and Moessbauer spectroscopy at various temperatures including strong external magnetic fields applied to the absorber. It was found that isomer shift exhibits sharply defined increase at about 105 K leading to the lowering of the electron density on iron nucleus by 0.02 electron/a.u.^3. Above jump in the electron density is correlated with the transition from the P4/nmm to the Cmma structure, while decreasing temperature. Moessbauer measurements in the external magnetic field and for temperatures below transition to the superconducting state revealed null magnetic moment on iron atoms. Hence, the compound exhibits either Pauli paramagnetism or diamagnetic behavior. The principal component of the electric field gradient on the iron nucleus was found as negative on the iron site.Comment: 9 pages, 6 figures, 1 tabl

NMR (55\text{}^{55}Mn, 139\text{}^{139}La) and Mössbauer Spectroscopy (119\text{}^{119}Sn) Studies of (La0.67\text{}_{0.67}Ca0.33\text{}_{0.33})(Mn1−x\text{}_{1-x}Snx\text{}_{x})O3−δ\text{}_{3-δ} Compounds

A $\text{}^{119}$Sn Mössbauer spectroscopy and zero field $\text{}^{55}$Mn and $\text{}^{139}$La NMR studies of (La$\text{}_{0.67}$Ca$\text{}_{0.33}$)(Mn$\text{}_{1-x}$Sn$\text{}_{x}$)O$\text{}_{3-δ}$ (x=0, 0.01, 0.03, andδ≈0.06) were reported. The temperature evolution of the Sn hyperfine field (B$\text{}_{hf}$) for x=0.03 determined from the Mössbauer spectroscopy measurements was analysed within a molecular field model. A fit to the temperature dependence of B$\text{}_{hf}^{max}$ provided the Curie temperature T$\text{}_{C}^{*}$=160(3) K, which is in good agreement with T$\text{}_{C}$ obtained from dc magnetisation measurements. The $\text{}^{55}$Mn NMR spectra for $x=0$ and 0.01 show a single double exchange Mn$\text{}^{3+}\text{}^{/}\text{}^{4+}$ resonance line and exhibit strong Suhl-Nakamura relaxation effects characteristic of the ferromagnetic metallic phase. The spectra for x=0.03 show a coexistence of the double exchange line with the lines characteristic of Mn$\text{}^{3+}$ and Mn$\text{}^{4+}$ valence states. This shows that a 3% Sn doping strongly suppresses the double exchange interaction and leads to microscopic phase segregation into ferromagnetic metal and ferromagnetic insulator