High-temperature magnetic investigations on uranium compounds

ウラン化合物における高温磁気特性研究

Galatanu, A.; 芳賀 芳範   ; 松田 達磨; 池田 修悟; 山本 悦嗣  ; 青木 大*; 竹内 徹也*; 大貫 惇睦

Galatanu, A.; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yamamoto, Etsuji; Aoki, Dai*; Takeuchi, Tetsuya*; Onuki, Yoshichika

これまでわれわれが育成したウラン化合物について、温度800Kまでの高温磁化率測定を行った。これらの磁化率測定の結果から、ウラン化合物では5f電子状態が局在的なものからパウリ常磁性的なものまで極めて幅広い磁性がみられるが、室温以上の十分高温では、局在的なキュリーワイス則に従う振舞いに、ほとんどの物質が回復することが明らかになった。セリウム化合物と比べると、局在的な振舞いは比較的高温であることも明らかとなった。

We investigated the magnetic property of typical uranium compounds by measuring the magnetic susceptibility in an extended temperature range up to about 800 K. The magnetic susceptibility follows the Curie-Weiss law for a localized 5-electron compound UPd and a ferromagnetic insulator UFeP. In most of the investigated compounds we observed a crossover effect of the 5 electrons from a low-temperature itinerant nature to a high-temperature localized one. This is found to be characteristic for ferromagnetic superconductors such as UGe and UIr, and also for antiferromagnets like USb or UNiSb. To assess an extension of this characteristic property in the uranium compounds we also investigated typical 5-itinerant compounds like UGa and UPtGa. The crossover effect is essentially important in heavy fermion compounds such as UPt, UPdAl and URuSi. Even in the paramagnetic compound of UB, the magnetic susceptibility is not temperature-independent, but approaches a 5-localized tendency at high temperatures. Since the samples were single crystals, we were also able to trace the evolution of the magnetic anisotropy. The high-temperature anisotropic susceptibility data were analyzed on the basis of the crystalline electric field scheme.