層状金属間化合物Gd_<1-x>La_xMn_2Ge_2の特異な磁性と伝導現象(II) : Gd_<0.925>La_<0.075>Mn_2Ge_2の示す多階段メタ磁性転移と巨大磁気抵抗

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In this work, we studied the magnetic and transport properties of an intermetallic compound Gd_<0.925>La_<0.075>Mn_2Ge_2 with a ThCr_2Si_2-type layered structure. Gd_<0.925>La_<0.075>-Mn_2Ge_2 exhibits canted ferrimagnetism with ferromagnetic and antiferromagnetic components below T_<t1>=348K.With decreasing temperature, it moves into a non-collinear antifirromagnetic state at T_<t2>=244K, and finally transforms into a reentrant canted ferrimagnet at T_<t3>=142K. For T_<t3>T<T_t2>, a field induced metamagnetism from antiferromagnetism to ferrimagnetism occurs at relatively lower fields, accompanied with fractal like multi-step metamagnetic transitions, the so called "devil's stair-case". The appearance of such fractal like multi-step metamagnetic transitions may result from a step-like formation of ferrimagnetic clusters due to spin-flips of Mn moments that occur independently in the antiferromagnet when magnetic fields are applied as well as from a step-like growth of their ferrimagnetic clusters. In addition, a giant magnetoresistance effect (△ρ / ρ〜15%) was also observed at the metamagnetic transition.
社団法人日本磁気学会の論文
2000-04-01