Refrigerant capacity of FeCrMoCuGaPCB amorphous alloys

Abstract

The magnetocaloric effect of the FeCrMoCuGaPCB alloy series, suitable for being prepared as bulk amorphous alloys, has been studied. Optimal refrigeration cycles have a cold reservoir close to room temperature. The refrigerant capacity of these alloys is comparable to that of a Mo-containing Finemet-type alloy and is ϳ40% bigger than that of other bulk amorphous alloys with comparable working temperatures. Analysis of the field dependence of the magnetic entropy change evidences a power law for all the magnetic regimes.

A constant magnetocaloric response in FeMoCuB amorphous alloys with different Fe∕B ratios

“…5 shows the thermal dependence of n for the different studied alloys. In agreement with previous experimental data, [15][16][17][18][19] the general behavior consists in ͑a͒ a value of n close to 1 for temperatures well below the transition temperature ͑b͒ a smooth decrease of n down to values close to 0.75 at T pk , and ͑c͒ a subsequent increase to n =2 in the paramagnetic region. These values have been ascribed 23 to ͑a͒ the temperature independent magnetization for moderate magnetic fields at low temperatures, ͑b͒ a relationship between n and the two critical exponents controlling the field dependence of magnetization at the Curie temperature ͑␦͒ and the thermal dependence of magnetization ͑␤͒, of the form n =1+͑1/␦͒͑1−1/␤͒, and ͑c͒ a consequence of the linear field dependence of magnetization where the Curie-Weiss law is valid, respectively.…”

“…[9][10][11][12][13][14][15][16] Albeit the maximum magnetic entropy change, ͉⌬S M pk ͉, for these alloys is modest when compared to that of rare-earth-based materials, the remarkable difference in material costs is an incentive for studying their suitability as magnetic refrigerants. Besides their reduced magnetic hysteresis ͑virtually negligible͒, the high electrical resistivity ͑which would decrease eddy current losses͒, tunable Curie temperature, and, in the case of bulk amorphous alloys, [17][18][19][20] outstanding mechanical properties are beneficial characteristics for a successful application of the material.…”

“…18 A similar effect has been observed for Cr and/or Mo substitution in bulk amorphous alloys. 19 Therefore, the application of hightemperature magnetic refrigerants would require the search for alloying elements which would optimize the Curie temperature of the material without a detrimental effect on the MCE response. Moreover, composites with a constant entropy change between the hot and cold reservoirs have been considered among the optimum materials for active magnetic regenerative refrigerators.…”

Enhanced magnetocaloric response in Cr∕Mo containing Nanoperm-type amorphous alloys

“…In particular, there is a growing interest in studying the applicability of soft magnetic amorphous alloys as magnetic refrigerants [9][10][11][12][13][14][15][16][17][18][19][20] due to their reduced magnetic hysteresis ͑vir-tually negligible͒, higher electrical resistivity ͑which would decrease eddy current losses͒, and tunable Curie temperature T Curie . Among the different compositional series of soft magnetic amorphous alloys, Nanoperm-type alloys are those that currently exhibit the highest RC values, having also among the highest values of ͉⌬S M pk ͉.…”

Magnetocaloric effect in Mn-containing Hitperm-type alloys

“…8 More recently, soft magnetic amorphous alloys are getting increasing attention as low-cost candidates for magnetic refrigeration. [9][10][11][12][13][14][15][16][17][18] ͑According to a well-known bibliographic database, more than 36% of the literature on the magnetocaloric effect in amorphous materials were published since 2005. Considering only the magnetocaloric effect in transition-metal-based amorphous alloys, more than 50% of the papers studying these materials were published since then.͒ Although the maximum magnetic entropy change, ͉⌬S M pk ͉, for these alloys is modest when compared to that of rare-earth-based materials, 1,6 the remarkable difference in material costs is an incentive for studying their suitability as magnetic refrigerants.…”