Magnetic anisotropy and phase transitions in single-crystal Tb5(Si2.2Ge1.8)

Abstract

<p>The Tb₅(Si_<em>x</em>Ge_{4−<em>x</em>}) alloy system has many features in common with the Gd₅(Si_<em>x</em>Ge_{4−<em>x</em>})system although it has a more complex magnetic and structural phase diagram. This paper reports on the magnetic anisotropy and magnetic phase transition of single-crystalTb₅(Si_2.2Ge_1.8) which has been investigated by the measurements of <em>M</em>-<em>H</em> and <em>M</em>-<em>T</em> along the <em>a</em>, <em>b</em>, and <em>c</em> axes. The variation of 1/<em>χ</em> vs <em>T</em> indicates that there is a transition from paramagnetic to ferromagnetic at <em>T</em>_<em>c</em> = 110 K. Below this transition temperature <em>M</em>-<em>H</em>curves show very strong anisotropy, and it is believed that this is due to the complex spin configuration. <em>M</em>-<em>H</em> measurements at <em>T</em> = 110 K show that the <em>a</em> axis is the easy axis, and that the saturation magnetization is 200 emu/g. The <em>b</em> axis is the hard axis, which needs an external magnetic field much higher than 2 T to saturate the magnetization in that direction, indicating a high magnetocrystalline anisotropy. The <em>c</em> axis is of intermediate hardness. The magnetic properties of this material are therefore very different from those of the related Gd₅Si₂Ge₂ system, in which the <em>b</em> axis was found to be the easy axis and the magnitude of the anisotropy was smaller.</p>