Magnetization in Mn-richγ−Cu100−xMnx (36<~x<~83)alloys in fields up to 75 kOe

Abstract

The field dependence of dc magnetization $[M(H)]$ has been measured in$\phantom{\rule{0ex}{0ex}}\ensuremath{\gamma}\ensuremath{-}{\mathrm{Cu}}_{100\ensuremath{-}x}{\mathrm{Mn}}_{x}$ ($x$=36, 60, 73, 76, and 83) alloys in magnetic fields up to 75 kOe at different temperatures between 4.2 and 21 K. The $M(H)$ data are found to be almost linear with field beyond 10 kOe. This is expected since the present alloys are antiferromagnetically ordered. But, at lower fields $(H<10 \mathrm{kOe}),$ the variation is slower than linear. The change of slope in $M(H)$ beyond the critical field of 10 kOe is attributed to the spin-flop transition which marks the collapse of the helical spin structure and the onset of the linear spin-density-wave modulation. Another interesting observation is that the composition dependences of the magnetization and the electrical resistivity exhibit a minimum and a maximum, respectively, around $x=73$. This behavior is described in terms of the transition of magnetic structure from AF3 to AF1.