Ambient pressure colossal magnetocaloric effect tuned by composition in Mn1−xFexAs

Abstract

The magnetocaloric effect (MCE) is the basis for magnetic refrigeration, and can replace conventional gas compression technology due to its superior efficiency and environment friendliness. MCE materials must exhibit a large temperature variation in response to an adiabatic magnetic-field variation and a large isothermal entropic effect is also expected. In this respect, MnAs shows the colossal MCE, but the effect appears under high pressures. In this work, we report on the properties of Mn(1-x)Fe(x)As that exhibit the colossal effect at ambient pressure. The MCE peak varies from 285 K to 310 K depending on the Fe concentration. Although a large thermal hysteresis is observed, the colossal effect at ambient pressure brings layered magnetic regenerators with huge refrigerating power closer to practical applications around room temperature.

Comparative analysis of magnetic and caloric determinations of the magnetocaloric effect in Mn0.99Co0.01As

“…2(c), due to inadequate application of the Maxwell relation to the magnetization data, using the expression previously shown. The observed maximum value, −ΔS T,max = 138 J/kg·K for a field change of 6 T, is comparable to the literature values for Mn 1−x Fe x As [11] and Mn 1−x Cu x As [12]. On decreasing field, no spurious ΔS T peaks are obtained, since each demagnetization curve starts from a fully FM state in the phase transition region and only the data below 6 T are considered.…”

“…The compound was arc melted under argon atmosphere, then heat treated in a resistive furnace at 1,340 K, followed by annealing at 1,070 K and water quenched to ambient temperature, as described in detail elsewhere [11]. The Xray diffraction pattern at room temperature indicates that the sample crystalizes in a single hexagonal phase.…”

“…The MCE of MnAs and its derivatives, with slight substitutions of Fe, Cu, and Cr for Mn, or Si and Sb for As [3,[10][11][12][13][14][15][16], have been extensively studied using magnetization data. As a result of an incorrect application of the Maxwell relation, some fallacious conclusions saying that the MnAs-based compounds exhibit "huge" or "colossal" MCE (|ΔS T,max | ∼ 300 J/kg·K) were made [11,12,15]. In this paper, we report on a giant MCE at room temperature (∼295 K) in Mn 0.99 Co 0.01 As, using three different methods, i.e., isothermal magnetization, heat capacity, and direct measurements.…”

Stable magnetostructural coupling with tunable magnetoresponsive effects in hexagonal ferromagnets

“…These magnetoelastic transitions have been utilized in the intensive investigations of a large body of giant magnetocaloric materials [19][20][21][22][23][24][25][26][27] . In contrast, in typical FMMTs, the change of structural symmetries of austenite and martensite is remarkable [6][7][8][9][10][11] .…”

Magnetic transitions and magnetocaloric effects in Fe0.75Mn1.35As

“…The magnetic refrigeration based on magnetocaloric effect (MCE) has attracted a great deal of interest in the prospect of an energy-efficient and environment friendly alternative to the common vapor cycle refrigeration technology [1][2][3][4][5].…”