Investigation on the magnetocaloric effect in (Gd,Pr)Al2 solid solutions

Abstract

a b s t r a c tA theoretical and experimental investigation on the magnetocaloric properties of the rare earth pseudobinary compounds Gd 1 À n Pr n Al 2 is presented. The calculated isothermal entropy and adiabatic temperature changes under magnetic field variations from 0 to 2 T and from 0 to 5 T are in good agreement with the experimental data. For the Pr-concentrations n ¼ 0.25, 0.5 and 0.75 the experimental data present an inverse magnetocaloric effect which was theoretically predicted and associated with the competition between the opposite magnetizations of the Gd and Pr sublattices. The two-sublattice Hamiltonian used in the calculations takes into account the crystal field, exchange and Zeeman interactions.

Magnetic and Magnetocaloric Properties of (Gd1-xCex)Al2(x = 0, 0.25, 0.5, 0.75) Compounds

“…Table 1. The lattice parameter of undoped GdAl 2 (x = 0) is about 7.915 Å, which agrees with the literature value of 7.913 Å [15,27]. Ce substitution leads to an almost linear increase in the lattice parameter from 7.913 Å for x = 0 to 8.026 Å for x = 0.75.…”

“…In Ce-doped samples the linear increase in the lattice parameter may occur because the Ce atomic radius is larger than that of Gd. Similar variations in lattice parameters were reported for Gd 1-x Pr x Al 2 [15] and Er 1-x Dy x Co 2 [32] alloys, where the atomic radii of Pr and Dy are larger than those of the substituted atoms, as in the case of Gd 1-x Ce x Al 2 . Fig.…”

“…Recent studies have verified that intermetallic RAl 2 (R = rare earth) compounds with cubic Laves-phase could be promising candidates for magnetic refrigeration technology due to their relatively large magnetic entropy change [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Therefore, the magnetic and magnetocaloric properties of several intermetallic compounds, such as DyAl 2 [11,12], TbAl 2 [13], ErAl 2 [14], PrAl 2 [15][16][17] and GdAl 2 [18][19][20], and their alloys, such as Gd 1-x Pr x Al 2 [15], [18,25,26] and Gd-(Al 1-x Co x ) 2 [27], have recently been intensively investigated.…”

“…Therefore, the magnetic and magnetocaloric properties of several intermetallic compounds, such as DyAl 2 [11,12], TbAl 2 [13], ErAl 2 [14], PrAl 2 [15][16][17] and GdAl 2 [18][19][20], and their alloys, such as Gd 1-x Pr x Al 2 [15], [18,25,26] and Gd-(Al 1-x Co x ) 2 [27], have recently been intensively investigated. These recent studies have showed that the ground state for most intermetallic Laves compounds is ferromagnetic.…”

“…Jianqiu et al [27] have reported that the maximum magnetic entropy change of GdAl 2 is 4 J/kg K for a magnetic field of 2 T and the Curie temperature is 165 K. Despite the fact that its Curie temperature is relatively low compared to room temperature, GdAl 2 shows a relatively large MCE. In many previous studies on intermetallic Laves compounds (RAl 2 ), it has been shown that the Curie temperature can be adjusted by alloying with appropriate transition metal or rare-earth elements [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The relatively large MCE and adjustable Curie temperatures of intermetallic RAl 2 compounds make them attractive candidates for magnetic refrigeration.…”