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Recent progresses in exploring the rare earth based intermetallic compounds for cryogenic magnetic refrigeration

A mean-field model of a Heisenberg spin-glass with weak random anisotropy is solved. It is shown that an Ising-like phase transition in a finite magnetic field $H$ occurs at ${T}_{c}(H)\\ensuremath{\\sim}{T}_{c}(0)\\ensuremath{-}A{H}^{\\frac{2}{3}}$ in the limit of small $H$. The crossover to an Ising behavior occurs when $\\frac{D}{J}g{(\\frac{\\ensuremath{\\mu}H}{J})}^{\\frac{2}{3}}$, where $D$ and $J$ are the anisotropy and exchange coupling constants, respectively.

Phase Transition in a Szyaloshinksy-Moriya Spin Glass.

Recent progress in the magnetic and cryogenic magnetocaloric properties of RE2TMTM’O6 double perovskite oxides

Enhancement of magnetocaloric effect around room temperature in Zn0.7Ni0.3-xCuxFe2O4 (0 ≤ x ≤ 0.2) spinel ferrites

Exchange bias in a mixed metal oxide based magnetocaloric compound YFe0.5Cr0.5O3

We present a detailed study of structural, magnetic and thermodynamic properties of a series of Heusler alloys Fe2-xMnxCrAl (x = 0, 0.25, 0.5, 0.75 and 1). Structural investigation of this series is carried out using high resolution synchrotron X-ray diffraction. Results suggest that with increasing Mn concentration, the L21 structure of Fe2CrAl is destabilized. The DC magnetization results show a decrement in paramagnetic (PM) to ferromagnetic (FM) phase transition temperature (TC) with increasing Mn concentration. From the systematic analysis of magnetic memory effect, heat capacity, time dependent magnetization, and DC field dependent AC susceptibility studies it is observed that, Fe2CrAl exhibits cluster glass(CG)-like transition approximately at 3.9 K (Tf2). The alloys, Fe1.75Mn0.25CrAl and Fe1.5Mn0.5CrAl exhibit double CG-like transitions near Tf1 ~ 22 K, Tf2 ~ 4.2 K and Tf1 ~ 30.4 K, Tf2 ~ 9.5 K respectively, however, in Fe1.25Mn0.75CrAl, a single CG-like transition is noted at Tf2 ~ 11.5 K below TC. Interestingly, FeMnCrAl shows the absence of long ranged magnetic ordering and this alloy undergoes three CG-like transitions at ~22 K (Tf*), 16.6 K (Tf1) and 11 K (Tf2). At high temperatures, a detailed analysis of temperature response of inverse DC susceptibility clearly reveals the observation of Griffiths phase (GP) above 300 K (T*) in Fe2CrAl and this phase persists with Mn concentration with a decrement in T*.

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Exotic magnetic behaviour and evidence of cluster glass and Griffiths like phase in Heusler alloys Fe 2-x Mn x CrAl (0 ≤ x ≤ 1)

Evidence of large magnetic cooling power and double glass transition in Tb5Pd2

We report the results of our investigations on the influence of partial substitution of Er and Gd for Dy on the magnetic and magnetoelectric properties of DyFe0.5Cr0.5O3, which is known to be a multiferroic system. Magnetic susceptibility and heat capacity data, apart from confirming the occurrence of magnetic transitions at ~121 and 13 K in DyFe0.5Cr0.5O3, bring out that the lower transition temperature only is suppressed by rare-earth substitution. Multiferroic behavior is found to persist in Dy0.4Ln0.6Fe0.5Cr0.5O3 (Ln = Er and Gd). There is an evidence for magnetoelectric coupling in all these materials with qualitative differences in its behavior as the temperature is changed across these two transitions. Remnant electric polarization is observed for all the compounds. The most notable observation is that electric polarization is seen to get enhanced as a result of rare-earth substitution with respect to that in DyFe0.5Cr0.5O3. Interestingly, a similar trend is seen in the magnetocaloric effect, consistent with the existence of magnetoelectric coupling. The results thus provide evidence for the tuning of magnetoelectric coupling by rare-earth substitution in this family of oxides.

https://iopscience.iop.org/article/10.1088/0953-8984/28/42/426003/pdf

Mohit K. Sharma

Papers

Exchange bias in a mixed metal oxide based magnetocaloric compound YFe0.5Cr0.5O3

Exotic magnetic behaviour and evidence of cluster glass and Griffiths like phase in Heusler alloys Fe 2-x Mn x CrAl (0 ≤ x ≤ 1)

Evidence of large magnetic cooling power and double glass transition in Tb5Pd2

Effect of rare-earth (Er and Gd) substitution on the magnetic and multiferroic properties of DyFe0.5Cr0.5O3.

Magnetic and universal magnetocaloric behavior of rare-earth substituted DyFe 0.5 Cr 0.5 O 3