Magnetic Properties Of Eu8gaxge46-X (Nominal X=16, 14, And 12) Type-I Clathrates

Melt-spinning technique can widen the range of Ga content in Eu8Ga(x)Ge(46-x) type-I clathrate. In this paper, it was used to obtain Eu8GaxGe46-x with nominal 16 >= x >= 10. Three samples with nominal x = 16, 14, and 12 are discussed in detail. Their actual Ga contents detected by EDS are 14.3, 13.4, and 11.5, which is a relatively wide range that has not been reported before. The decrease of Ga content results in the decrease of lattice parameter a. Moreover, a huge decline of the ferromagnetic transition temperature T-C is observed. It is 34.7 K, 27.0 K, and 20.0 K for Eu8GaxGe46-x with nominal x =16, 14, and 12, respectively. However, the saturation magnetic moment mu(sat) and effective magnetic moment mu(eff) are not greatly affected by the change of Ga content. The decrease of T-C is mainly attributed to the decrease of molecular field coefficient lambda, which can be calculated by fitting the relation curve between exchange mean field H-exch and magnetization M. The fitted lambda values are 0.25, 0.18, and 0.16 for samples with nominal x = 16, 14, and 12. Because the decrease of T-C is beneficial to the increase of magnetic entropy change, the maximum value of magnetic entropy change (-Delta S-M(max)) around T-C when Delta H = 3 T increases from 6.0 to 7.0 J/(kg K) as x decreases from 16 to 12. (C) The Minerals, Metals & Materials Society and ASM International 2020