The effects of interstitial atoms H and B on magnetic properties and magnetocaloric effect in LaFe_11.5Al_1.5 compound

The changes in magnetic properties of LaFe_11.5Al _1.5H_x and LaFe_11.5Al_1.5B_y have been investigated. By introducing interstitial atoms H or B, the magnetic ground state is changed from the antiferromagnetic to the ferromagnetic state, accompanied by significant increases in the saturated magnetization (Ms) and the Curie temperature (T_C). An attractive feature is that the magnetic transition from the second-order to the weakly first-order with increasing hydrogen content compared to the magnetic transition from the weakly first-order to the second-order with increasing boron content. The maximum magnetic entropy change (-ΔS_M) under a field change of 0-5T increases from 10.1J/kg·K for hydrogen content x=0.12 to 12.3J/kg·K for x=1.3, while decreases from 9.6J/kg·K for boron content y=0.1 to 9.2J/kg·K for y=0.3.