Magnetic properties of Y1−xTbxMn6Sn6 alloys

Abstract We have made low- and high-field magnetization measurements and neutron diffraction experiments on Y 1− x Tb x Mn 6 Sn 6 alloys with the hp13-type structure. YMn 6 Sn 6 ( x =0) shows an inhomogeneous helical antiferromagnetism with the Neel temperature of 333 K. The magnetization shows a steep increase in a field of 20 kOe and approaches saturation around 110 kOe. The alloys with x ⩾0.2 have the spontaneous magnetization. The magnetization curves show saturation around 40 kOe. The Curie temperature is 347 K for x =0.2 and increases with increasing x . It is likely that the magnetic moments of Mn (=2.0 μ B /Mn atom) and Tb (=9.0 μ B /Tb atom) are antiferromagnetically coupled to each other. At low temperatures around 12 K, the spin direction for the alloy with x =0.2 deviates slightly from the c -axis, and the small components on the c -plane have a helical structure with a propagation vector parallel to the c -axis. This structure transforms to a different type of helical structure above 160 K.