Magnetocrystalline anisotropy in single crystal Gd$_{5}$Si$_{2.7}$Ge$_{1.3}$

We have determined the magnetocrystalline anisotropy, easy and hard axes and the anisotropic constants for single crystal Gd$_{5}$Si$_{2.7}$Ge$_{1.3}$ using magnetization vs. angle of rotation and magnetization vs. magnetic field measurements carried out on a vibrating sample magnetometer (VSM). Magnetization was measured as a function of angle with an applied field of 0.12~MA/m (1500~Oe) in the `ab', `bc' and `ca' planes with angles measured from the `a', `c' and `c' axes respectively. It was determined from the measurements that the `b' axis has the highest susceptibility and hence is the easy axis, while the `a' and `c' have lower and approximately equal susceptibilities and hence are the hard axes. The magnetic anisotropy energy E$_{an}$ was calculated using E = $\mu _{0}$HM. The first order uniaxial anisotropic constant K$_{1}$ was determined by fitting the E$_{an}$ vs. $\theta $ curve to uniaxial anisotropy energy equation E$_{an}$ = K$_{1}$sin$^{2}\theta _{ }$and was determined to be 1.451$\times $10$^{4}$~J/m$^{3}$. This research is supported by the Royal Society under a Wolfson Research Merit Award.