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SUMMARY:Inelastic neutron scattering and µSR investigations of an anisotr
 opic hybridization gap in the Kondo insulators: CeT2Al10 (T=Fe\, Ru and Os
 ) - Dr. Adroja Devashibhai\, ISIS Facility\, Rutherford Appleton Laborator
 y
DTSTART:20180307T111500Z
DTEND:20180307T123000Z
UID:TALK97609@talks.cam.ac.uk
CONTACT:Romy Hall
DESCRIPTION:The recent discovery of topological Kondo insulating behaviour
  in strongly correlated electron systems has generated considerable intere
 st in Kondo insulators both experimentally and theoretically. The Kondo se
 miconductors CeT2Al10 (T=Fe\, Ru and Os) possessing a c-f hybridization ga
 p have received considerable attention recently because of the unexpected 
 high magnetic ordering temperature of CeRu2Al10 (TN=27 K) and CeOs2Al10  (
 TN=28.5 K) and the Kondo insulating behaviour observed in the valence fluc
 tuating compound CeFe2Al10 with a paramagnetic ground state down to 50 mK 
 [1-6].  We are investigating this family of compounds using inelastic neut
 ron scattering (INS) and µSR measurements to understand the role of aniso
 tropic c-f hybridization on the spin gap formation as well as on their mag
 netic properties. We have observed a clear sign of a spin gap in all three
  compounds from INS  study as well as the existence of a spin gap above th
 e magnetic ordering temperature in T=Ru and Os. Our INS studies on single 
 crystals of CeRu2Al10 and CeOs2Al10 revealed dispersive gapped spin wave e
 xcitations below TN [6]. Analysis of the spin wave spectrum reveals the pr
 esence of strong anisotropic exchange\, along the c-axis (or z-axis) stron
 ger than in the ab-plane. These anisotropic exchange interactions force th
 e magnetic moment to align along the c-axis\, competing with the single io
 n crystal field anisotropy\, which prefers moments along the a-axis. In th
 e paramagnetic state (below 50 K) of the Kondo insulator CeFe2Al10\, we ha
 ve also observed dispersive gapped magnetic excitations which transform in
 to quasi-elastic scattering on heating to 100 K [4-7]. I will discuss the 
 origin of the anisotropic hybridization gap in CeFe2Al10 based on theoreti
 cal models of heavy-fermion semiconductors [8-10].  Further the effect of 
 electron- and hole-doping as well as chemical pressure effect on the magne
 tic and transport properties of CeT2All0 compounds will be discussed based
  on our INS and µSR results [5]. Our µSR study reveals a long range magn
 etic ordering for electron doping in the Kondo insulator CeFe2Al10. I will
  compare the results of our INS study with that of topological Kondo insul
 ators.\n \n  \n[1] A. M. Strydom\, Physica B 404\, 2981 (2009).\n[2] Y. Mu
 ro et al\, Phys. Rev. B 81\, 214401 (2010).\n[3] D.D. Khalyavin et al\, Ph
 ys Rev. B 82\, 100405(R) (2010).              \n[4] D.T. Adroja et al\, Ph
 ysica Scripta\, 88\, 068505\, (2013).\n[5] D.T. Adroja et al\, Phys Rev. B
 \, 87\, 224415 (2013)\; \n     D.T. Adroja et al\, Phys Rev. B 92\, 094425
  (2015).            \n[6] D.T. Adroja et al\, Solid State Phenomena\, 257\
 , 11\, (2016)\; arXiv:1607.06538v1\n[7] J.M. Mignot et al\, B 89\, 161103(
 R) (2014).\n[8] H. Ikeda and K. Miyake\,  J. Phys. Soc. Japan\, 65\, 1796 
 (1998). \n[9] P.S. Riseborough\, J. Mag. Mag. Mat. 226-230\, 127 (2001).\n
 [10] P.S. Riseborough and S.G.Magalhaes\, J. Mag. Mag. Mat. 400\, 3 (2016)
 .\n
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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