Herrero-Albillos Julia, García Luis Miguel, Bartolomé Fernando
Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK.
J Phys Condens Matter. 2009 May 27;21(21):216004. doi: 10.1088/0953-8984/21/21/216004. Epub 2009 Apr 29.
A systematic x-ray magnetic circular dichroism study of the paramagnetic phase of ErCo(2) has recently allowed us to identify the inversion of the net magnetization of the Co net moment with respect to the applied field well above the ferrimagnetic ordering temperature, T(c). The study of small-angle neutron scattering measurements has also shown the presence of short range order correlations in the same temperature region. This phenomenon, which we have denoted parimagnetism, may be related to the onset of a Griffiths-like phase in paramagnetic ErCo(2). We have measured ac susceptibility on ErCo(2) as a function of temperature, applied field and excitation frequency. Several characteristics shared by systems showing a Griffiths phase are present in ErCo(2), namely the formation of ferromagnetic clusters in the disordered phase, the loss of analyticity of the magnetic susceptibility and its extreme sensitivity to an applied magnetic field. The paramagnetic susceptibility allows us to establish that the magnetic clusters are only formed by Co moments as well as the intrinsic nature of those Co moments.
最近对ErCo₂顺磁相进行的一项系统的X射线磁圆二色性研究，使我们能够确定在远高于亚铁磁有序温度T(c)时，Co净磁矩的净磁化强度相对于外加磁场的反转。小角中子散射测量研究也表明在相同温度区域存在短程有序关联。我们将这种现象称为顺磁体磁性，它可能与顺磁态ErCo₂中类似格里菲斯相的出现有关。我们测量了ErCo₂的交流磁化率随温度、外加磁场和激发频率的变化。ErCo₂呈现出一些具有格里菲斯相的系统所共有的特征，即在无序相中形成铁磁团簇、磁化率解析性的丧失及其对外加磁场的极端敏感性。顺磁磁化率使我们能够确定磁性团簇仅由Co磁矩形成，以及这些Co磁矩的固有性质。
