Magnetocaloric effect in bulk amorphous Pd40Ni22.5Fe17.5P20 alloy

Abstract

We have studied the temperature (T) and field (H) dependence of the magnetocaloric effect in a bulk amorphous Pd40Ni22.5Fe17.5P20 alloy. With decreasing T, and depending on H, the alloy exhibits superparamagnetic, field-induced ferromagnetic, and spin-glass behavior. The temperature-dependence of the magnetic entropy change, ΔS=S(H)−S(H=0), exhibits extreme values: a minimum at the superparamagnetic-to-ferromagnetic transition and a maximum at the ferromagnetic-to-spin-glass transition. At 80 K, and for H=50 kOe, the entropy change is −0.029 kB per Fe atom in the alloy. This value compares favorably with that measured in other crystalline and amorphous Fe-based alloys, but it is lower than that measured in some rare-earth elements.

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.…”

Influence of Co addition on the magnetocaloric effect of FeCoSiAlGaPCB amorphous alloys

“…However, there are few studies concerning the magnetocaloric response of bulk amorphous alloys. 16 It has been shown that the Co addition to this family of alloys produces a decrease of its Curie temperature, T C am . 14 Therefore, this compositional change could be a way for tuning the ⌬S M peak temperature.…”

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 ͉.…”