DiSalvo, F. J.

Hambourger, Paul D.

English

Cleveland-Marshall College of Law

Cleveland State UniversityEngagedScholarship@CSUPhysics Faculty Publications Physics Department1978Magnetoresistance of 1T-TaSe2Paul D. HambourgerCleveland State University, p.hambourger@csuohio.eduF. J. DiSalvoFollow this and additional works at: https://engagedscholarship.csuohio.edu/sciphysics_facpubPart of the Physics CommonsHow does access to this work benefit you? Let us know!Publisher's StatementCopyright 1978 American Institute of Physics. This article may be downloaded for personal use only.Any other use requires prior permission of the author and the American Institute of Physics. Thefollowing article appeared in Bulletin of the American Physical Society 23 (1978): 245-245 and may befound at http://www.aps.org/meetings/baps/.Repository CitationHambourger, Paul D. and DiSalvo, F. J., "Magnetoresistance of 1T-TaSe2" (1978). Physics Faculty Publications. 126.https://engagedscholarship.csuohio.edu/sciphysics_facpub/126This Article is brought to you for free and open access by the Physics Department at EngagedScholarship@CSU. It has been accepted for inclusion inPhysics Faculty Publications by an authorized administrator of EngagedScholarship@CSU. For more information, please contactlibrary.es@csuohio.edu.Original CitationHambourger, Paul D. and F. J. DiSalvo. "Magnetoresistance of 1T-TaSe2." Bulletin of the American Physical Society 23 (1978): 245-245.them decrease with incY'easing x. Weattribute this behavior to stY'ong coupling between these modes and the CDW:*work supported In paY't by the NSF. 1 f.J. Di Salvo, D.E. Moncton, and J.V. Waszczak Phys. Rev. B 14,4322 (1976). 2 J.A. Holy, K.C. Woo, M.V. Klein, and F.C. Drown, Phys. Rev. B~, 3628 (1977), eeB ~l.§..§.~1.£_PrQE~f.!l~~_of 2H-TaSe , J. L. FELDMAN, C. L. VOLD, andE":--'F:--sK"tLTON, Naval Research Laboratory, and Shu-Cheng YU andtL. SPAIN, University of Maryland--The elastic constants, ~n partic~lar c ,of the layeredTM~chalcogenlde mater~als at~ of interest for the interpretation of stress dependent informa­tion. In order to obtain it is useful toc 13combine linear fompressipUity values with neutron-measured (zero sound) elastic con­stants. In this paper both pressure and tempera­ture dependences of the lattice parameters are determined from x-ray diffraction measurements. A force model would be required to estimate zero sound-isothermal elastic constant differences arising from anharmonicity. The fact that we find from our thermal expansivities that isother mal-adiabatic elastic constant differences are negligible suggests that it is reasonable to combine our linear compressibili ties with the zero sound el~stic f£nstants. T~us we obtain ~1.5<c 3<3, ~n 10 dynes/em. Estimates )f Gru~~.isen parameters, the Debye temperature, 'nd straln dependences of the ICDW. transition emperature will also be discussed. . D. E. Moncton, J. D. Axe, and F. J. Di Salvo, Phys. Rev. B16, 801 (1977). CC9 Magnetoresistance of IT-TaSe2 . P. D. .WlBOURGER, Cleveland State U., and F. J. DiSALVO, lell Laboratories. --The transverse magnetoresistance )f single-crystal IT-TaSe2 has been measured at T=4.2K :.n magnetic fields up to 23 kG with J..L[OOOlJ. Al­~hough the observed magnetoresistance was quite small (ApJp 'V 0.015), substantial anisotropy was observed. \t 22 kG, Ap/p was l\J 40% larger for BJ.. [OOOlJ than for Y/IoOOlJ. The anisotropy is therefore the reverse of that observed in 2H-TaSe2 (ref. 1) and 2H-NbSe2 (ref. nand suggests that in the presence of the charge density wave the Fermi surface of IT-TaSe2 may not be dominated by cylinders parallel to [0001] as is the case in 2H-TaSe2 (refs. 1,3) and probably also in 2H-NbSe2 (ref. 2). lp. D. Hambourger, Phys. Rev. B15, 1640 (1977). 2p. D. Hambourger and N. E. Lewis, (abstract submitted for ~he Charge Density Wave Symposium , University of Wa1'1~lck, January, 1978). 3J. E. Graebner, Solid State Commun. 31., 353 (1977). CClO Electronic Structure and Lattice Instabilities in IT-TiSAg and IT-V5e:a .* A.J. FREEMAN, Northwes tern U. and Argonne, and A. ZUNGER**, Northwestern U.--A first principles self-consistent band structure calculation on IT-TiSell shows that a constant volume variation of the internal crystal parameter z (which determines the metal-nonmetal layer separation and the Ti-Se bond dis­tance) produces an electronic phase transition from the nomal semi-metal to a semi-conductor. Since a 2% r:duction uncrosses the p-d band overlap at L,and Since the observed bond shortening is 2.4%, such a phase transition may account for the observed decrease in conductivity and susceptibility in the em state. In VSea we find that the p-d band overlap increases and the volume of the electron Fenni surface decreases ~apidly as the (anomalously large) cia ratio decreases. ~ ~ model in which the em instability is associated W~t d-band nesting, smaIL changes in c/a would dras­t1cally affect the magnitude of the nesting q and con­~quentlY the transition temperature. upported by NSF, AFOSR, and USDOE ~CGl1 Phonon Sp,:ctra in l-T TiSe~. N. WAKABAYASHI and F'C' ~M6TH, Oa~ Rldse National Lab. ,)'; and K.C. WOO and •. R WN, Unlv. of Illinols.--Phonon frequencies of ~eve ra 1 branches for the I aye red compound l-T TI Se', have teen measured along f-M and A-L directions by slo\~-neu­ro~ scattering techniques. Mixing of acoustic and' °bPtlchcharacters of modes seems to exist for various ranc es. Dispersion c . h .d urves In t e f-M direction mea­s~re l~t 50 Kand room temperature have been found to s ow I ttle difference. Special attention I'las paid to trans ve rse modes hav In th l' .to e g e po arlzatlon vectors parallel ffh . layer. At the L point where a super lattice re ec~i~n exists below 200 K, a phonon has been observed to exhibit a temperature dependence \'1hich may bt~ ex­pected for a soft mode. HOI'lever, no diffUSe' scatterinq w~s observable near L possibly due to the small si1mple' size. A lattice dynamical model has been constructed to Interpret these results as well as the results obtained ~ecently by Moncton et al. 1 Operated by Union Carbide Corporation for the Departmentof Energy. ID. E. ~onc:on, F. J. DiSalvo, and J. D. Axe, private commun I cat I on. CC 12 Su erlattice Formation in 4Hb-TaSe, , J:R. Duf ey, R.D. K1rby,h . o. Nebras "a- 2 L1ncoln, R.V. Coleman, U. of Vlr,1n1a, --- The 4Hb-polytype of TaSe cons1sts 0 alternating2lay:=Y's <?f octahedral and trigonal prismatic co­ordlnatlon. A Charge density wave (CD\oJ) commen­surate state transition occurs in the octahedral layeY's at ~lOoK, while the trigonal prismatic layeY's undergo 8 t1ansition to an incon~ensuY'ate CDW stat5 at 75 K. Our Raman measurements a~o~e 75 K show a low frequency spectrum very s1mllar ~o that obser~ed in the IT-polytype gfTaSe 2 ) wlth many CDW ~nduced lines. Below 7S K, a bY'0~1 temperatUl;e depen~ent mode occurs near 40 cm . vJe attY'lbute thls mode to an ampli­tude mode of the coupled CDW-lattice. Its behav­ior is very similar to the incommens~rate state amplitude mode observed in 2H-TaSe 2 . * WOY'k supported in paY't by NSF 1 F.J. Di Salvo) D.E. Aoncton, J.A. Wilson, and . S. Mahajan, ?hys. Rev. B 14,1543 (1976). 2 E. F. SteigmeieY') G. riarbeke, H. Auderset, and F.J. Di Salvo, Solid State Commun. 20,667(1976 CC 13 Quantum Oscillatory Effects in 2H-TaS2.'* S. J. HILLENIUS and R. V. eOLEl'IAN. Univ. of Virginia. --Quantum oscillations have been studied in 2H-TaS2 using both the Shubnikov de Haas and de Haas van Alphen effect. The observed frequencies are in the range .04 to 6 MG and correspond to Fermi surface sections in the clmrge density wave state of the crystal. Four of the strongest frequencies follow a two dimensional angular dependence described by WI/sin e while others show an angular dependence more characteristic of three dimensional Fermi surface sections. Comparison to results on 4Hb-TaSz shows a comparable range of frequencies in both phases but different precise values and dimensional behavior are observed. The perfect 2H phase crystals were produced by thermally transforming 4Hb-TaS2 crys­tals and the measurements have been made in the range 0-150 kG. *Work supported by U.S. DOE contract EY-76-S-05-3l0S. CC 14 Press-ure Derivative Sign Reversal for Proton Spin-Lattice Rela.xationTimes in Ta.s2~.!..* H.T. WEAVER, J.E. SCHIRBER, Sandia Labs., and B.G.SILBERNAGEL, Exxon Research.--Proton spin-lattice relaxation times (Tl~ have been measured for the intercalculated compound TaS2'NH3 as a function of tempera.ture (77"'S. T ~ 300K) and pressure to 6 kbar. Pressure effects on Tl were sufficiently large that the sign reversal for dTr/dP, which is predicted by simple diffusion models, is ob­served. The temperatures at which dTr/dP changes sign (T = 190K) and TI is minimum are within experimenta.l 245 

Magnetoresistance of 1T-TaSe2

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Magnetoresistance of 1T-TaSe2

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