Metamagnetic transition and the anomalous virgin magnetization curve in Ce(Fe0.96Ru0.04)2

We present results of dc magnetization measurements investigating the magnetic field-induced metamagnetic transition in Ce(Fe 0.96 Ru 0.04 ) 2 . In the temperature region where this material undergoes a ferromagnetic to antiferromagnetic first-order phase transition, the isothermal virgin magnetization curve lies distinctly outside the envelope magnetization curve obtained in the subsequent field cycles. We show that this anomalous behaviour of the virgin magnetization curve arises due to the dependence of the initial zero field magnetic state on the temperature–field history of the sample in the concerned temperature regime. This origin of the anomalous virgin magnetization curve is distinctly different from the very similar behaviour observed earlier in Al- and Os-doped CeFe 2 alloys, where this feature was associated with the kinetic arrest of the first-order ferromagnetic to antiferromagnetic transition.