Magnetic properties and magnetocaloric effect of LaFe11.5−xTxSi1.5 (T = Cr, Ni)

Abstract

Magnetic properties and magnetocaloric effects of LaFe11.5−xTxSi1.5 (T = Cr, Ni; x = 0, 0.1, 0.15, and 0.2) have been investigated by magnetic measurements and differential scanning calorimetry and compared with that of Mn, Co substitution. The Curie temperatures (TC) of LaFe11.5−xCrxSi1.5 compounds are decreased from 193 K (x = 0) to 185 K (x = 0.2) with increasing Cr. Although the latent heat and relative cooling power are slightly decreased by Cr doping, the first-order magnetic transition is preserved, which lead to a large entropy change about 21 J/kg·K for all the Cr substituted samples. In contrast, Ni only concentrates in La-rich phase, and due to the decrease of Fe/Si ratio in the main phase by Ni doping, the TCs of LaFe11.5−xNixSi1.5 compounds increase from 193 K (x = 0) to 206 K (x = 0.2) with increasing Ni amount, and the nature of magnetic transition is changed from first order to second order resulting in the decrease of entropy change.

Solid solubility in 1:13 phase of doping element for La(Fe,Si)13 alloys

“…Wang et al found that the the Curie temperature, latent heat, relative cooling power and magnetic entropy change would all decrease with the partial substitution of Cr (x < 0.2) for Fe in LaFe 11.5−x Cr x Si 1.5 , but the first order magnetic transition remains unchanged. 4 Moreover, the partial substitution of Mn for Fe in La(Fe,Si) 13 based alloys would also cause a decrease in both Tc and magnetic entropy change value, 5 which is similar to the results in Cu-doped alloys. 6 On the whole, the partial substitution of 3d-transition elements for Fe in La(Fe,Si) 13 based alloys would reduce the magnetic entropy change, and the nature of magnetic transition would change from first order to second order in some cases.…”

“…1 So far, the effect of element substitution for Fe on the magnetic properties of La(Fe,Si) 13 alloys has been investigated extensively. [2][3][4][5][6][7] For La(Fe 0.99 Z 0.01 ) 11.4 Si 1.6 (Z = Ni, Cu, Cr, V) alloys, it is found that the Curie temperature (Tc) of the matrix alloy would increase while the magnetic entropy change value would decrease by doping Z elements. 3 In addition, the nature of magnetic transition of the alloy changed from first order to second order by the introduction of Ni element.…”

Zero thermal expansion in NaZn13-type La(Fe,Si)13 compounds

“…This small increase of T c could be attributed to the change in the density of 3d states (Nd) at the Fermi level (EF) due to the different number of electrons contributed from Si to the conduction band compared with that of Fe. 20,26 Furthermore, the Fe I -Fe II distance plays a critical role in the exchange interaction. 20,21 With increasing Si content, the Fe I -Fe II distance increases because of the smaller atomic size of Si compared with that of Fe, which promotes the positive exchange interaction and may break the long-range magnetic order in Fe and help to form local magnetic domains.…”

Microstructure and magnetocaloric effect in as‐quenched GdGeSi alloys with addition of Ni and Ce

“…Investigations of these materials are mainly focused on preparation of alloys with large MCE in the vicinity of room temperature, which can be used in cooling technology . It has been shown in several papers that addition of small amount of impurities can affect their performance. Moreover, long term heat treatment leads to creation of desired phases, which significantly increase MCE.…”