Magnetocaloric effect in Co-rich Er ( Co 1 − x Fe x ) 2 Laves phase

Magnetic properties and magnetocaloric effect (MCE) in Co rich Er ( Co 1 − x Fe x ) 2 have been studied by magnetic measurements and electronic structure calculations. With increasing x from 0 to 0.2, T C increases from 32 to 360 K and the magnetization decreases from 6.8 μ B to 5.3 μ B per formula unit ( 5 K ) , respectively. The peak value of the magnetic entropy change decreases rapidly from 23.0 to 4.5 J ∕ kg K (under an external field change of 5 T ) with increasing x from 0 to 0.1. The addition of a small amount of Fe in Er Co 2 drives the order of magnetic transition from first order to second order, as evidenced by the magnetothermal curves around T C , which is responsible for the decrease in MCE. The magnetic moment dependence of total energy E t ( m ) is studied by a fixed spin moment band structure calculation. E t ( m ) for x = 0 has two minima at a low and a high Co magnetic moment, which correspond to a metastable and a stable magnetic state, respectively. On the other hand, E t ( m ) for x = 0.125 shows only one minimum at a high Co (Fe) magnetic moment. These fixed spin moment calculation results explain the observed change in the order of magnetic transition by the addition of Fe in Er Co 2 .