The magnetic phase diagram and the effect of pressure on the magnetic properties of the Y1-xGdxMn2 intermetallic compounds

The magnetization up to 50 kOe, the magnetic susceptibility under external pressure up to 5 kbar and the thermal expansion of the cubic Laves phase co mpounds Y1-xGdxMn2 were studied over a wide temperature range. Two well def ined concentration regions were isolated in the x-T phase diagram: 0 less t han or equal to x < 0.2, in which the antiferromagnetic structure is primar ily determined by the d-d interaction (YMn2-type), and 0.2 < x less than or equal to 1, in which the f-d interaction plays a dominant role (GdMn2-type ). It is concluded that both the Gd and the Mn sublattices are ordered in G dMn2 below T-N = 108 K, the change in the magnetic characteristics at 40 K being interpreted as an antiferromagnetism-non-collinear ferrimagnetism tra nsition. The intermediate Y0.8Gd0.2Mn2 compound shows a freezing and time-d ependent behaviour at low temperatures characteristic of shea-range order. The effects can also be induced by external pressure at higher Gd concentra tions.