Structure, magnetic and magnetothermal properties of the non-stoichiometric ErCo2Mnx alloys

Abstract

The structure, magnetic and magnetothermal properties and heat capacity of the ErCo2Mnx (0 ≤ x ≤ 1.4) non-stoichiometric alloys have been studied. It is shown that the alloys with x ≤ 0.8 are almost single-phase with the MgCu2-type Laves-phase structure, while the alloys for x ≥ 1.0 contain considerable amount of the cubic Th6Mn23-type phase. Alloying with manganese leads to a substantial increase in the exchange interactions. For the binary ErCo2 compound, the magnetization shows a first-order magnetic phase transition with the Curie temperature TC = 35 K. For all the Mn-containing alloys studied, the transition is found to be the second-order type; the Curie temperature in ErCo2Mnx sharply growths with increasing x and reaches its maximum value 212 K for the ErCo2Mn0.6 alloy. Using the magnetization data and the results of the heat capacity measurements, we estimated the magnetocaloric effect for these compounds. The obtained results are discussed on the assumption of a strong variation of the 3d-metal magnetic moments upon alloying with Mn.