QUANTUM EFFECT IN MAGNETISM

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Magnetism of Ce and U intermetallic compounds were investigated focused on quantum effects.(1)Spin-lattice coupling was studied on Ce(Ru_<085>Rh_<015>)_2Si_2 and U_2Rh_3Si_5 by mens of thermal expansion and magnetostriction. 4f^1 electron of Ce ion in Ce(Ru_<085>Rh_<015>)_2Si_<2 > changes from localized to itinerant state due to Kondo effect. The change of electronic state induces volume change. Such a volume change is interpreted as an INVAR like effect in heavy fermion system.(2) Magnetism of tiny moment in UPt_3 and URu_2Si_2 were studied theoretically.(3)Stability of ferromagnetism in (In, Mn)As semiconductor was studied.(4)There are 3 critical boundaries between antiferromagnetic and paramagnetic states which are at x = 0.03, 0.4 and 0.5 in Ce(Ru1_<1-X>Rh_X)_2Si_2. Fermi and non-Fermi liquid behaviors appear at the lowest temperatures for x = 0.03 and for x = 0.4 and 0.5, respectively. These behaviors were studied by muSR and a magneitc phase transition at T = 0 is suggested for x = 0.03 while , for x = 0.4 and 0.5, a Griffiths like phase is proposed which has a negative T_N.