Ferri-to-ferro-magnetic and ferro-to-para-magnetic transitions in Ni48Co2Mn35In13Ga2 Heusler alloy

Abstract

Heusler alloys feature both conventional and inverse magnetocaloric effects near room temperature as they undergo two different transitions. In this paper, new data are presented and analyzed and a new mechanism to explain the complex hysteretic behavior of a Ni48Co2Mn35In13Ga2 Heusler alloy is developed. This mechanism explains isothermal loops near room temperature. The various descriptions and classifications of these transitions, however, is not critical to this analysis.

Room temperature magnetocaloric effect in Mn1.25Fe1.75Ga Heusler alloys

“…The data on this alloy are consistent with those of Ref [20], in which two peaks were observed in these curves; a positive peak which represents the first mixed state (ferrimagnetic to ferromagnetic) and a negative peak (ferromagnetic to paramagnetic) which represents the second mixed state.…”

“…The room-temperature crystal structure was characterized by X-ray diffraction (XRD) with Cu Ka radiation. The XRD patterns show that the as-made ribbons have the L21 cubic structure (Figure 2) which is a typical structure for Heusler alloys [19][20][21] .…”

“…From Figure 6(a), as the applied field is increased from 0.1 to 10 kOe, the intensity of the positive peak increases and then decreases when the applied field increases from 10 to 30 kOe. In typical Heusler alloys 20 , the δM/δT curves can be related with two transition temperatures, a ferri-to ferromagnetic (the positive maximum of δM/δT) and a ferro to paramagnetic (Curie temperature) ( Figure 6(b)). As shown in Fig.…”

“…The intense research activity over the past fifteen years on room-temperature magnetic refrigeration has led to the discovery of numerous performing magnetocaloric materials with working temperature around 300 K. Previous studies have shown that the Ni-Mn-Ga alloys are common candidates as magnetic refrigerant materials. In these materials the transition temperature TC can be tuned to be near room temperature [6][7][8][9][10][11][12][13] by adjusting the Ni:Mn ratio, adding another element such as In, and annealing at high temperatures for long time [19][20][21] . In earlier work in 1997, it was reported by Gschneidner et.al.…”

Realization of Enhanced Refrigeration Capacity with Non-Hysteretic Behavior in Ni40Gd5Co5Mn37In12Si1 Alloy Near Room Temperature at 2T

“…To be specific, pure elemental Gd has regarded to be a state-of-the-art material that exhibits the maximum RC of ∼402 at 5 T near SOPT with non-hysteretic characteristics near room temperature . Furthermore, Pecharsky and Gschneidner have also reported the giant MCE in the intermetallic alloy of Gd 5 Si 2 Ge 2 with the RC of 640 J kg –1 and Δ S M of ∼9.4 J kg –1 K –1 under 5 T which is notably high as compared to elemental Gd. , Particularly, a few class of materials exhibits high MCE in the FOPT region with large RC values and distinguishable hysteretic nature, such as Gd 5 Si 2 Ge 2 , LaFe 13– x Si x H, MnFeP 0.45 As 0.55 , MnAs 1– x Sb x , Co 50 Ni 22 Ga 2 , and Ni–Mn-based Heusler alloys, − whereas some group of materials show notably good RC values in the SOPT region with almost non distinguishable thermal hysteretic character such as Gd 60 Fe 20 Al 20 , EuTiO 3 , Pr 0.7 Ca 0.3 Mn 0.95 Cr 0.05 O 3 , and so on. However, most of materials that show large MC response near SOPT in the proximity of the room-temperature range are either expensive or low-abundant which indeed limits their practical applications.…”