Metamagnetic transition and magnetocaloric effect in ErCo₂

Abstract

The magnetization MH(T) and the specific heat capacity cP,H(T) of the ErCo2 intermetallic compound were measured in the temperature range 5 - 100 K and in 0, 7 or 14 T applied field, respectively. A clear first-order phase transition is found at the magnetic ordering of the Er sublattice. While for order-disorder transitions in simple ferromagnets there is a good agreement between magnetocaloric performance predicted on the basis of magnetization measurements compared to calorimetric measurements, it is necessary to investigate whether the agreement is still present for materials with more complex transitions (e.g. order - order, metamagnetic, first order etc). From the magnetization data the magnetic entropy change at the transition was calculated using the Maxwell relations. From the cP,H(T) measurements both the magnetic entropy change and the adiabatic temperature change were calculated and compared to values obtained from MH(T) and to the values calculated by the usual approximative expressions. The agreement is less good than in the case of second-order phase transitions. The discrepancy is interpreted in terms of the theory of first-order/metamagnetic transitions showing that the boundary conditions used in the derivation of the approximative formulae for simple ferromagnetic materials are not appropriate for more complex transitions as in ErCo2.

Universal behavior for magnetic entropy change in magnetocaloric materials: An analysis on the nature of phase transitions

“…13,14 Moreover, the large entropy change showed by ErCo 2 has led to studies on the MCE properties of the pure and pseudobinary Co Laves phases. 2,[15][16][17][18][19][20][21][22] We have also selected the ferromagnetic manganites, La 2/3 ͑Ca x Sr ͑1−x͒ ͒ 1/3 MnO 3 with x = 0, 0.5, and 1, in order to give more generality to our results. The physical properties of these materials have been reported in literature.…”

μSR study of short-range magnetic order in the paramagnetic regime of ErCo2

“…[1][2][3][4] In particular, the study of the Co band has been the subject of intense investigation for decades. [5][6][7][8][9][10][11][12][13] In these compounds, the Co sublattice is near the critical condition for the formation of magnetic moment, turning the Co 3d-electron system very sensitive to the internal field created by the R sublattice or to changes of external parameters. Particularly unique is the case of the Co sublattice in ErCo 2 , as it is just above the condition for undergoing a metamagnetic transition.…”

“…Particularly unique is the case of the Co sublattice in ErCo 2 , as it is just above the condition for undergoing a metamagnetic transition. 1,7,14,15 The ErCo 2 structure is cubic above the first-order ferrimagnetic ordering transition (T c = 32 K at H = 0 T), which has an associated rhombohedral distortion of the crystal structure. 16 The magnetic behavior of the compound is mostly dominated by the Er sublattice at all temperatures.…”

Specific Heat and Magnetocaloric Effect in Ho-Er-Co Solid Solutions

“…It should be noted that MCE properties of HoCo 2 and ErCo 2 were investigated. According to Tishin et al [10] for HoCo 2 the maximum T ad at 84 K reaches 10 K for a field change µ 0 H of 10 T. Giguere et al [11] reported the maximum T ad = 14.4 K for ErCo 2 at 33 K for µ 0 H = 14 T. In the case of Ho 1 − x Er x Co 2 some theoretical calculation was performed by Oliveira et al [12]. They have shown that the introduction of Er ions decreases the magnetic ordering temperature of the pseudobinary compounds and the nature of the magnetic phase transitions continues to be first-order for all Er concentrations.…”