The effects of Ni substitution on magnetic and magnetocaloric effect (MCE) are investigated in polycrystalline Y-type hexaferrites of Sr2Zn2-xNixFe12O22 (x = 0.0, 0.8, and 2.0). With the increasing of temperature, the M-T curves indicate successive magnetic structure transitions exist in Sr2Zn2-xNixFe12O22 (x = 0.0, 0.8, and 2.0), which play significant roles in MCE behaviors. As the Ni2+ doping ratio increases, the shape of −ΔSM−T curves near room temperature evolves gradually from a table-like to a peak-like form. Particularly, a significant contrast between CMCE and IMCE is observed below 100 K, whose behavior can be inherently exploited for heat sink in magnetic refrigeration applications. Among the samples in this series, Sr2Zn1.2Ni0.8Fe12O22 plays the best CMCE and IMCE performances, with the maximum magnetic entropy change (−ΔSMmax) values of 0.78 J/kg K at 354 K and −0.56 J/kg K at 16 K for ΔH=50kOe , respectively. Our work demonstrates that Sr2Zn2-xNixFe12O22 hexaferrites have great potential to be tailored for magnetic refrigeration with special needs such as different operating temperature zones, Ericsson cycle or heat sink at refrigeration.

中文翻译：

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Ni取代Y型Sr2Zn2-xNixFe12O22六铁体中的逆和常规双磁热效应


研究了 Ni 取代对磁热效应 （MCE） 的影响在 Sr2Zn2-xNixFe12O22 （x = 0.0、0.8 和 2.0） 的多晶 Y 型六铁氧体中。随着温度的升高，M-T 曲线表明 Sr2Zn2-xNixFe12O22 中存在连续的磁性结构转变 （x = 0.0、0.8 和 2.0），这在 MCE 行为中起着重要作用。随着 Ni2+ 掺杂比的增加，接近室温的 -ΔSM-T 曲线形状逐渐从表状演变为峰状。特别是，在 100 K 以下观察到 CMCE 和 IMCE 之间的显着差异，其行为本身可以用于磁制冷应用中的散热器。在该系列样品中，Sr2Zn1.2Ni0.8Fe12O22 的 CMCE 和 IMCE 性能最佳，当 ΔH=50kOe 时，最大磁熵变 （−ΔSMmax） 值分别为 0.78 J/kg K，在 16 K 时为 −0.56 J/kg K。我们的工作表明，Sr2Zn2-xNixFe12O22 六铁素体具有很大的潜力，可用于满足特殊需求的磁制冷，例如不同的工作温度区、爱立信循环或制冷散热器。