A magnetization study of ErMn6Sn6-xGax single crystals (0.11 <= x <= 1.20)

Dc and ac magnetic measurements have been performed on single crystals of HfFe6Ge6 type ErMn6Sn6-xGax compounds prepared by the flux method. At low temperature all the compounds display easy-axis magnetization and undergo a spin reorientation transition to easy-plane magnetization below room temperature. The complete ferrimagnetic order (?sat = 4 ?B fu-1) is reached at 10 K only in the easy direction. From low field magnetization measurements at 10 K, a first order magnetic process (FOMP) has been detected for all the compounds and ascribed to the competition between the higher order magnetocrystalline terms. An additional transition detected from the imaginary part of the ac susceptibility for the x = 0.85 and 1.20 compositions was explained in terms of displacement of Bloch walls. The anisotropy constants, evaluated, following the Sucksmith and Thompson method, for some compositions at room temperature, decrease at increasing Ga content.