Magnetoelastic Coupling and Cryogenic Magnetocaloric Effect in Two-Site Disordered GdSrCoFeO₆ Double Perovskite

Abstract

The development of new magnetic refrigerants demands an effective investigation of materials with a large magnetocaloric effect in a wide temperature range. Herein, we report on the structural, magnetic, and magnetocaloric properties of the two-site disordered double perovskite GdSrCoFeO 6 prepared by the modified solid-state synthesis method. Temperature-dependent synchrotron X-ray diffraction analysis revealed that GdSrCoFeO 6 crystallizes in the orthorhombic phase (Pnma), with Gd 3+ /Sr 2+ and Co 2+/3+ /Fe 3+/4+ ions randomly distributed on the A-and B-sites, respectively. An observed lattice parameter anomaly around 60 K indicates the occurrence of the magnetoelastic coupling, which coincides with the presence of ferro/ferrimagnetic (FM/FiM) ordering below T C ≈ 65 K from the magnetic measurements. These results match well with our first-principles calculation prediction of low-temperature magnetic (FM/FiM) and electronic (insulating/metal) transitions related to a combined effect of Co and Fe shortand long-range competitions, crossings of spin state at Co ions, and the hybridization degree between Gd-4f and Co-3d states. Additionally, a modified Arrott plot and Kouvel−Fisher analysis were used to establish the nature of the magnetic phase transition in GdSrCoFeO 6 , yielding the critical exponent β = 1.46(6)/1.45(6), γ = 1.48(5)/1.17(2), and δ = 2.01(3)/1.80(5), respectively. The specific heat analysis reveals two well-defined broad peaks (∼10 and ∼70 K), which match well with a Schottky anomaly (Gd-4f) and the magnetic transition of FM/FiM to paramagnetic order, respectively. The magnetocaloric effect (MCE) analysis reveals a maximum magnetic entropy change ΔS M max ≈ 13 J kg −1 K −1 (at ∼8 K) under a field of 0−7 T. These results evidence that the Schottky anomaly and the magnetoelastic coupling seem to be key factors for driving further enhancements to the MCE in GdSrCoFeO 6 , making it a possible candidate for cryogenic applications.

Temperature dependent structural properties of Mn1.90M0.10O3 (M = Cr and Fe)

“…The temperature evolution of these parameters is shown in figure 4(c). The change in the lattice parameters at the magnetic ordering is referred as magnetoelastic coupling and reported in many other systems also [38,39]. This supports the correlation between structural and magnetic properties and magnetoelastic coupling in the studied sample.…”

Magnetocaloric Properties in Rare-Earth-Based Metal–Organic Frameworks: Influence of Magnetic Density and Hydrostatic Pressure

“…On the other hand, even if the Ho ion has a greater J = 8 ( S = 2 and L = 6), the corresponding MOF only yields a −Δ S M max of 3.71 J/kg·K at 17 K. Thus, from the magnetization point of view, we observed that PM moment and M S play an important role in enhancing the magnetic entropy change values in the α-RPF-4 series. Also, as the magnetoelastic effect is the result of a strong interaction between the lattice and the magnetic interactions, the magnetic entropy change is associated with the short-range magnetic interaction of ions in the system, which is intensified by changes in bond length and the lattice reorganization upon cooling …”

“…On the other hand, these n values depend on the magnetic transition temperature and the critical exponents of each compound, although further studies would be needed in this regard. From the −Δ S M ( T ) curves, we have calculated the relative cooling power (RCP) expressed as RCP = |Δ S M max | × δ T fwhm (δ T fwhm is full width at half-maximum) . The δ T fwhm was obtained for the maximum curves at Δ H = 0–7 T through Lorentzian adjustments.…”

“…Also, as the magnetoelastic effect is the result of a strong interaction between the lattice and the magnetic interactions, the magnetic entropy change is associated with the short-range magnetic interaction of ions in the system, which is intensified by changes in bond length and the lattice reorganization upon cooling. 22 For materials that display a second-order phase transition, the field dependence of the maximum magnetic entropy change follows a power law as −ΔS M max ≈ H n , where n is the critical exponent related to magnetic ordering. 23 The fitting of the whole series is shown in Figure S5, yielding n values that range between 0.1 and 0.49.…”

“…From the −ΔS M (T) curves, we have calculated the relative cooling power (RCP) expressed as RCP = |ΔS M max | × δT fwhm (δT fwhm is full width at half-maximum). 22 The δT fwhm was obtained for the maximum curves at ΔH = 0−7 T through Lorentzian adjustments. The RCP values that we obtained as a function of the rare-earth ionic radii are plotted in Figure 4.…”