Magnetic and magnetocaloric properties of DyCo2Cx alloys

Abstract

The magnetic and magnetocaloric properties of DyCo2Cx (x = 0, 0.05, 0.1, and 0.15) alloys were investigated. The results show that the Curie temperature (TC) of the DyCo2Cx alloys increases with increasing C content, from 136 K (x = 0) to 152 K (x = 0.15), but the lattice parameter a of DyCo2Cx exhibits a maximum at x = 0.05. The suppression of the ac susceptibility of DyCo2Cx at low temperature indicates the enhancement of the domain wall pinning effect by carbon doping. The positive slops of the Arrott plots of the doped compounds indicate that the phase transition is second order for the carbon-doped alloys, and the maximum value of the isothermal magnetic entropy change (ΔSM) for the magnetic field change of 50 kOe decreases from −13.9 J/kg• K (x = 0) to −7.8 J/kg•K (x = 0.15). The relative cooling power (RCP) of DyCo2Cx is nearly the same in all studied alloys, while the temperature-averaged entropy change over 10 K temperature span, TEC(10), indicates decreasing magnetocaloric performance of carbon doped materials.

Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Bulk Manganites La0.7Ba(0.3−x)CaxMnO3 (x ≤ 0.25)

“…This is explained by the existence of local minima and maxima on Initial observation reveals that the value for TEC for all polycrystalline samples diminishes with increasing temperature span ∆T H-C . This tendency has been reported in previous research [51][52][53] and is expected, as the graphs for magnetic entropy change in bulk have a smooth Gaussian-like distribution. Nano-sized samples, on the other hand, show a small fluctuation around a mean value, which also diminishes, but very slowly, with increasing ∆T H-C .…”

“…A wide temperature range is neglected as a worthwhile figure, and even books on magnetocaloric effects omit δT FW HM completely [50]. For this purpose, temperature-averaged entropy change (TEC) is seen by many as a more suitable figure-of-merit [51,52]:…”

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si)13-Based Compounds

“…Despite this behavior, the herein achieved pressure-dependent Δ s T maxima of 28, 28, 25, and 15 J (kg K) −1 at 0, 0.3, 0.5, and 0.8 GPa, respectively, are at approximately T > 70 K, still larger compared to the purely magnetocaloric effect of La­(Fe,Si) 13 -type, ,, Fe 2 P-type, , and Mn 3 GaC , compounds, Ni­(–Co)–Mn–X Heusler alloys (X = Sn, , Sb–In, Ti), and numerous highly resource critical, rare-earth containing materials. − However, it should be noted that the pressure-assisted magnetocaloric effect of the La 0.7 Ce 0.3 Fe 11.6 Si 1.4 compound is not able to surpass at approximately T < 70 K the currently best performing heavy rare-earth-based compounds. ,− This highlights also the aforementioned limitation of utilizing the first-order magnetostructural phase transition of La 0.7 Ce 0.3 Fe 11.6 Si 1.4 at such low temperatures, as minimum magnetic field changes of 4 T are required to induce the phase transition, and the hysteresis leads to irreversibility at T < 50 K (Figure (c)), thereby emphasizing the need for a tailored hysteresis to operate at such low temperatures . A graphical representation of the aforementioned comparison of Δ s T is shown in Figure S5 with additional information in Table S1.…”

Tuning phase transitions and optimization of the magnetocaloric effect in Ho(Co&lt;sub&gt;1&ndash;&lt;/sub&gt;&lt;sub&gt;&lt;italic&gt;x&lt;/italic&gt;&lt;/sub&gt;Mn&lt;sub&gt;&lt;italic&gt;x&lt;/italic&gt;&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt; alloys

“…然而, 由于其一级相变的 特性, 这些材料在居里温度附近存在一定的热滞和磁 滞, 这对于磁制冷来说是不利的. 目前已有不少工作 研究了元素掺杂对RCo 2 (R=Er, Ho, Dy)合金的居里温 度和磁热效应的影响 [19][20][21] , 但是如何调节相变类型使 其获得巨磁热效应和小磁滞损耗的研究尚未见报道. 本文研究了Mn部分替代Co对Ho(Co 1−x Mn x ) 2 合金 的晶体结构、磁相变和磁热效应的影响.…”