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

Abstract The structure, magnetic and magnetothermal properties and heat capacity of the ErCo 2 Mn x (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 MgCu 2 -type Laves-phase structure, while the alloys for x  ≥ 1.0 contain considerable amount of the cubic Th 6 Mn 23 -type phase. Alloying with manganese leads to a substantial increase in the exchange interactions. For the binary ErCo 2 compound, the magnetization shows a first-order magnetic phase transition with the Curie temperature T C  = 35 K. For all the Mn-containing alloys studied, the transition is found to be the second-order type; the Curie temperature in ErCo 2 Mn x sharply growths with increasing x and reaches its maximum value 212 K for the ErCo 2 Mn 0.6 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 3 d -metal magnetic moments upon alloying with Mn.