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UIr was shown recently to be one of the rare ferromagnets, which becomes superconducting under pressure when the ferromagnetic phase is destroyed [1]. Because enhanced critical ferromagnetic fluctuations are believed to induce superconductivity in such systems, an understanding of the magnetic properties might be crucial to explain superconductivity. We present here an ambient pressure study of UIr by magnetization, magnetostriction, thermal expansion, and specific heat, for magnetic fields applied along the easy axis c [2]. The critical ferromagnetic regime, which extends surprisingly up to several Tesla, is analyzed using Arrott and Maxwell relations. The uniaxial pressure dependences of the Curie temperature TC and of the saturated moment Ms are also extracted from our data. Non-universal critical exponents are obtained and the role of magnetic anisotropy is emphasized by our analysis. A connection is made to existing Moriya-like spin fluctuations theories [3,4], and we propose that such theories might be developed, in the light of our results, for real and thus anisotropic systems.
[1] T. Akazawa et al. J. Phys.: Condens. Matter 16, L29 (2004). [2] W. Knafo et al, arXiv:0807.4411v1 [cond-mat.str-el] [3] T. Moriya and T. Takimoto, J. Phys. Soc. Japan 64, 9605 (1995). [4] Y. Takahashi and T. Kanomata, Mater. Trans. 47, 460 (2006). |
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