Magnetic and magnetocaloric properties of the ternary Gd-based metallic glasses Gd60Mn30X10, with X = Al, Ga, In

Magnetocaloric effect and refrigeration capacity (RC) of Gd60Mn30Ga10 and Gd60Mn30In10 melt-spun nanocomposites are investigated. It is found that the nanocrystallites formed in the amorphous matrix are different between melt-spun Gd60Mn30Ga10 and Gd60Mn30In10 samples. Gd60Mn30Ga10 ribbons exhibit multiple second-order transitions in accordance to their composite nature whereas Gd60Mn30In10 ribbons display only one magnetic transition. The occurrence of several transitions increases the gap of temperature at half maximum value of the ΔSM magnetic entropy, thus increasing the RC values of these materials. The use of Mn as transition metal induces Curie temperature values around 170–180 K and an antiferromagnetic coupling with Gd reducing the overall magnetization compared to that calculated considering the free Gd3+ ion.

Figure optionsDownload as PowerPoint slideResearch highlightsGd60Mn30In10 and Gd60Mn30Ga10 nanocomposites have been prepared by single-roller melt-spinning. In their temperature operating range, around 175–180 K, melt-spun Gd60Mn30In10 and Gd60Mn30Ga10 samples exhibit refrigeration capacities of 451 and 472 J kg−1, respectively, in a field change of 4.6 T. Such values are rather good, if we consider their low ΔSM peak values. This enhancement is clearly due to the widening of the temperature range over which the two magnetic transitions occur by first, having a very large transition due to the amorphous phase and by combining this transition to that of nanocrystallites. Changing the X p-element between Al, Ga or In induced the formation of different nanocrystallites embedded in the amorphous matrix. Among them, only α-Gd displayed a magnetic transition (TC = 284 K) in melt-spun Gd60Mn30Al10 and Gd60Mn30Ga10 samples. On the contrary, melt-spun Gd60Mn30In10 sample displayed the amorphous matrix transition only probably because of the effect of a magnetic dead layer at the surface of crystallized nanoparticles of Gd(In) and Gd2In. An antiferromagnetic coupling between Gd and Mn is strongly suspected in these melt-spun materials. It seems, then, very interesting to investigate the impact of the transition metal on the overall behaviour in such samples with different M by means of magnetization measurements under high magnetic fields up to 70 T to observe the saturation of these Gd-based materials.