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

Abstract

A universal curve for the change in the magnetic entropy has been recently proposed for materials with second-order phase transitions. In this work we have studied the universal behavior of the magnetocaloric effect in the family of cobalt Laves phases, RCo 2 , and mixed manganites, La 2/3 ͑Ca x Sr ͑1−x͒ ͒ 1/3 MnO 3 , which exhibit first-and second-order phase transitions. The rescaled magnetic entropy change curves for different applied fields collapse onto a single curve for materials with second-order phase transition as opposed to the first-order phase transition compounds, for which this collapse does not hold. This result suggests that the universal curve may be used as a further criterion to distinguish the order of the phase transition.

Magnetocaloric effect and critical exponents of Fe77Co5.5Ni5.5Zr7B4Cu1: A detailed study

“…8 Moreover, the scaling laws and the universal curve for the magnetocaloric effect can also be used as an alternative to the Banerjee criterion 9 to determine the order of the phase transition only from magnetization measurements. 10 However, in some specific cases, experimental results of the field dependence of the magnetic entropy change seem to be inconsistent with the behavior predicted by the critical exponents. For example, in the case of FeCoNiZrBCu alloys, values of the exponent for field dependence of the peak magnetic entropy change can vary by $20% depending on the temperature steps used for the isothermal magnetization experiments when calculated either from the values of the critical exponents or from the nonlinear fitting of the peak magnetic entropy change versus field.…”

Identifying the critical point of the weakly first-order itinerant magnet DyCo2with complementary magnetization and calorimetric measurements

“…Nevertheless, in spite of the extensive work on this system, the details of the H-T phase diagram are much less established, and the critical point (where the first order transition disappears) has not previously been determined. 18,19,20 Here we study DyCo 2 using both magnetic and calorimetric methods -to investigate whether there is a giant enhancement of the heat capacity, C p , close to T c as previously observed in the La(Fe,Si) 13 system. 6,7 We obtain the latent heat and C p separately, so that we can also establish 3 the relationship between latent heat and hysteresis in this system.…”

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.…”