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The effects of sintering temperature (Ts) and chemical substitution on the structural and magnetic properties of manganite compounds L a 1 − x S r x M n 1 − y F e y O 3 (0.025 ≤ x ≤ 0.7 ; y = 0.01 , 0.15) are explored in a search to optimize their magnetocaloric properties around room temperature. A ferromagnetic (FM) to paramagnetic (PM) phase transition is observed at a Curie temperature Tc that can be controlled to approach room temperature by Sr and Fe substitution, but also by adjusting the sintering temperature Ts. Accordingly, the magnetic entropy change (− Δ S M ) quantifying the magnetocaloric effect (MCE) presents a peak at or close to Tc that shifts and broadens with both Sr and Fe doping and is further tuned with sintering temperature. Altogether, we show that it is possible to adjust the strength and dominance of the ferromagnetic coupling in these ceramics, but also using disorder as a tool to broaden and adjust the temperature range with a significant magnetic entropy change. [ABSTRACT FROM AUTHOR]

The effects of sintering temperature (Ts) and chemical substitution on the structural and magnetic properties of manganite compounds L a 1 − x S r x M n 1 − y F e y O 3 (0.025 ≤ x ≤ 0.7 ; y = 0.01 , 0.15) are explored in a search to optimize their magnetocaloric properties around room temperature. A ferromagnetic (FM) to paramagnetic (PM) phase transition is observed at a Curie temperature Tc that can be controlled to approach room temperature by Sr and Fe substitution, but also by adjusting the sintering temperature Ts. Accordingly, the magnetic entropy change (− Δ S M ) quantifying the magnetocaloric effect (MCE) presents a peak at or close to Tc that shifts and broadens with both Sr and Fe doping and is further tuned with sintering temperature. Altogether, we show that it is possible to adjust the strength and dominance of the ferromagnetic coupling in these ceramics, but also using disorder as a tool to broaden and adjust the temperature range with a significant magnetic entropy change. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of L a 0.85 S r 0.15 M n 0.99 F e 0.01 O 3 perovskite oxides are investigated in the framework of the mean-field theory with a goal to develop a comprehensive model with parameters that can be used to optimize the caloric performances for cooling applications. Using the experimental magnetic isotherms M(H,T), we estimate and compare the exchange parameter (λ) , the saturation magnetization (M 0) , the total angular momentum (J) , and the gyromagnetic factor (g) for two different samples annealed at 1170 and 1250 °C. These parameters are used, in turn, in the simulation of the magnetic and the magnetocaloric properties of these L a 0.85 S r 0.15 M n 0.99 F e 0.01 O 3 compounds assuming imperfect samples with compositional and/or magnetic inhomogeneities. For this purpose, a Gaussian distribution of the Curie temperature is assumed. The temperature dependence of the magnetic entropy change, − Δ S M (T) , resulting from an applied field variation is simulated for both samples. The selected distribution captures the rounding of the − Δ S M (T) peak at its maximum and its broadening with growth conditions, features that are constantly observed in many bulk polycrystalline compounds. [ABSTRACT FROM AUTHOR]

In previous studies, we have reported that double perovskite La2NiMnO6 presents non-negligible potential for room temperature magnetocaloric tasks. With the aim of improving even further the cooling performances and the working temperature range of double perovskites, we report the magnetic and magnetocaloric properties of La2MnFeO6 and ALaMnFeO6 (A = Sr, Ba, and Ca) compounds. X-ray diffraction and Rietveld refinement show that La2MnFeO6 (LMFO) and CaLaMnFeO6 (CLMFO) samples crystallize in an orthorhombic structure with the P n m a space group. However, a rhombohedral structure with the R 3 ¯ C space group is obtained for BaLaMnFeO6 (BLMFO) and SrLaMnFeO6 (SLMFO) samples. Substituting La by Ba or Sr in LMFO leads to a clear increase of the Curie temperature (Tc) compared to LMFO from 150 K for BLMFO up to 350 K for SLMFO. Moreover, CLMFO shows the smallest Tc down to 70 K. Ferromagnetic-like behavior is observed for SLMFO and BLMFO, while CLMFO's magnetism resembles that of LMFO. A clear connection between the structural parameters and the magnetic properties of these doped LMFO samples is unveiled as the highest Tc and the largest magnetization are observed for SLMFO which also shows bond angles closest to 180° and the smallest bond lengths, thus optimizing the superexchange interaction. The partial substitution of Sr for La leads, in fact, to a significant magnetocaloric effect over a wide operating temperature range extending beyond 300 K. For some optimal growth conditions, its entropy change varies slowly over an unusually large temperature range, which is of clear interest from a practical point of view. [ABSTRACT FROM AUTHOR]

Combining multiple degrees of freedom in strongly correlated materials such as transition-metal oxides would lead to fascinating magnetic and magnetocaloric features. Herein, the strain effects are used to markedly tailor the magnetic and magnetocaloric properties of PrVO3 thin films. The selection of an appropriate thickness and substrate enables us to dramatically decrease the coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to 0.05 T for compressive thin films making from the PrVO3 compound a nearly soft magnet. This is associated with a marked enhancement of the magnetic moment and the magnetocaloric effect that reaches unusual maximum values of roughly 4.86 μB and 56.8 J/kg K with the magnetic field change of 6 T applied in the sample plane in the cryogenic temperature range (3 K), respectively. This work strongly suggests that taking advantage of different degrees of freedom and the exploitation of multiple instabilities in a nanoscale regime is a promising strategy for unveiling unexpected phases accompanied by a large magnetocaloric effect in oxides. [ABSTRACT FROM AUTHOR]

Recently, a reversible and a giant rotating magnetocaloric effect has been pointed out in the multiferroic TbMn2O5 single crystal, opening the way for new designs of low-temperature magnetic cooling. In this paper, we report a preliminary theoretical work with the aim of enlarging our understanding on the electronic, magnetic and accordingly magnetocaloric features of the TbMn2O5 compound. Particularly, the TbMn2O5 magnetic anisotropy is analyzed in terms of X-ray magnetic circular dichroism (XMCD) and X-ray absorption spectroscopy (XAS) spectra. [ABSTRACT FROM AUTHOR]

In this paper, we report on the magnetic properties and magnetocaloric effect (MCE) in NaZn13-type LaFe11.2Co0.7Si1.1Cx (x=0.1 and 0.3) close to room temperature. The Landau theory as well as the temperature dependence of magnetization data revealed that LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3 exhibit a second-order magnetic transition near their Curie temperature. We have calculated the magnetocaloric effect both in terms of isothermal entropy change and adiabatic temperature change using the magnetization and the direct measurements. Under an external field change from 0 to 5 T, -ΔS is 14.5 J/kg K (TC=290 K) and 8 J/kg K (TC=310 K) for x=0.1 and 0.3, respectively. The calculated refrigerant capacity for a field change in 0-5 T is about 305 and 286 J/kg K, for LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3respectively, which is larger than that of some magnetocaloric materials with a first-order phase transition (Gd5Ge2Si2). ΔTad decreases with increasing C content. It was found to be about 1.5 for x=0.1 and 1.2 for x=0.3 under 1.48 T. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the influence of the rare earth element (R) on the physical properties of RVO 3 (R = Er, Ho, Y, Lu). For this purpose, a theoretical work is reported in this study using ab initio method with the intent of enhancing our knowledge of the electronic, and magnetic properties of RVO 3 (R = Er, Ho, Y, Lu) compounds. The electronic properties of these materials show the presence of Jahn-Teller effect, with a band gap of approximately 0.58eV, 1.57eV, 1.12eV, 1.28eV, for ErVO 3 , HoVO 3 , YVO 3 , LuVO 3 , respectively. The magnetic contribution of Ho, Er, and V atoms in HoVO 3 , and ErVO 3 compounds was disentangled using X-ray magnetic circular dichroism (XMCD). The magnetic anisotropies of RVO 3 with (R = Er, Ho, Y, Lu) are studied and analyzed using spin orbit coupling. We noticed an easy axis of magnetization along the c-direction with strong magneto-crystalline anisotropy energies for the non-magnetic rare earth elements (R = Lu, Y)VO 3. For the magnetic rare earth elements, the easy and hard magnetization direction were found to be along b-axis and c-axis, and a-axis and c-axis for HoVO 3 , and ErVO 3, respectively. This means that instead of the standard magnetization demagnetization process, large thermal effects can be obtained by spinning their single crystals in constant magnetic fields. The exchange coupling between (Ho–V) is also found to be greater than the other exchange interactions in HoVO 3. Accordingly, a large conventional magnetocaloric could be created in HoVO 3 , since the Ho Ising moments experience a metamagnetic transition. However, the magnetocaloric effect (MCE) is expected to be lower in ErVO 3 due to the weak (Er–V) exchange coupling. • Structural, electronic, and magnetic properties of RVO 3 (R = Er, Ho, Y, Lu) are investigated by DFT calculations. • Strong magnetocrystalline anisotropy is pointed out in RVO 3 (R = Er, Ho, Y, Lu). • Large rotating magnetocaloric effects are expected in RVO 3 (R = Er, Ho, Y, Lu). • The (Ho–V) exchange coupling is found to be much larger than the (Er–V) interplay. • The magnetocaloric effect is expected to be less pronounced in ErVO 3 than HoVO 3. [ABSTRACT FROM AUTHOR]

Large rotating magnetocaloric effect (MCE) has been recently observed in HoMn 2 O 5 single crystals due to the strong magnetocrystalline anisotropy making a significant step towards efficient magnetic refrigeration systems. We tried to explain, theoretically, the reasons behind the magnificent performance in terms of magnetocaloric effect based on DFT calculations and Monte Carlo simulations. X-ray magnetic circular dichroism (XMCD) was performed in order to disentangle the magnetic contribution responsible for the MCE, as well as, the investigation of electronic and magnetic properties. The obtained results would enable the understanding of electronic and magnetic behaviors experimentally observed in HoMn 2 O 5 single crystals and the optimization of their MCE for magnetic refrigeration application. • Magnetic properties and magneto-caloric effect (MCE) in HoMn 2 O 5 single crystals were studied. • Large values of − Δ S M and RCP were observed at low temperature by Monte Carlo simulations. • The origin of MCE in Δ S M in HoMn 2 O 5 was discussed. • First principle study was performed to investigate the magnetic contribution and the anisotropy in HoMn 2 O 5. [ABSTRACT FROM AUTHOR]

We report on the structural, magnetic and transport properties of Pr 2 CuMnO 6 prepared by the solid-state reaction method. X-ray diffraction and Rietveld refinement reveal an orthorhombic crystal structure (space group Pnma) with no trace of secondary phases in the prepared samples. FC and ZFC magnetization measurements show a second order ferromagnetic to paramagnetic (FM-PM) phase transition at 35 K confirmed further through investigations using the universal master curve and Arrott plots. The partial Cu-Mn ordering and lack of long-range order in the system are indicated by the absence of magnetic saturation up to a magnetic field of 7 T down to 5 K. A reversible magnetic entropy change (− Δ S m ) with a maximum value of 1.47 Jkg − 1 K − 1 and a relative cooling power of 96.37 Jkg − 1 at the applied field of 7 T are observed around T c. [ABSTRACT FROM AUTHOR]

• The impact of Mn 2 O 3 secondary phase on the morphology, and physical properties of La 0.6 Ca 0.4 MnO 3 material was investigated. • When Mn 2 O 3 is mixed with the La 0.6 Ca 0.4 MnO 3 compound, SEM micrographs show an increase in the grains size. • The Mn 2 O 3 addition has no impact on the Curie temperature of the composites. • For 20% of Mn 2 O 3 , the refrigerant capacity can be enhanced by more than 20% when compared to that shown by the mother compound. Perovskite manganite (1−x)La 0.6 Ca 0.4 MnO 3 /xMn 2 O 3 (x = 0, 0.05. 0.1, 0.15, 0.20) composites were prepared by solid state reaction method. X-ray diffraction measurements were used to confirm the crystal structure and the average crystallite size of the samples. Their magnetic, magnetocaloric and heat capacity properties display a presence of second order magnetic phase transition at 260 K. The maximum magnetic entropy change was found to be 5.33 J/kgK for x = 0.1 of Mn 2 O 3 under 5 T. The relative cooling power (RCP) was found (235 J/kg) to largely exceed that reported in early works for a similar family of materials. In addition, the RCP of the mother alloy is enhanced by more than 20% under 32 kOe without affecting the Curie temperature that remains approximately constant close to 260 K. Our results suggest that the addition of Mn 2 O 3 could be useful for the enhancement of the LCMO refrigerant capacity without affecting the Curie temperature. [ABSTRACT FROM AUTHOR]

• Production of (La 0.45 Nd 0.25)Sr 0.3 MnO 3 /0.05CuO by pilot scale spray drying method. • A new ways for the enhancement of the magnetocaloric effect in (La 0.45 Nd 0.25)Sr 0.3 MnO 3 /0.05CuO, based composite materials. • High magnetic entropy change (2. J/kg·K at 2 T) was observed in (La 0.45 Nd 0.25)Sr 0.3 MnO 3 /0.05CuO. This study presents an investigation of the structural, magnetic and magnetocaloric properties of the 0.95(La 0.45 Nd 0.25)Sr 0.3 MnO 3 /0.05CuO polycrystalline composite. The investigated composite materials are elaborated by combining both solid-state reaction and spray-drying method at the pilot-scale aiming to obtain a homogeneous composite material with controlled morphology and regular particles size. The structure, microstructure, magnetism and magnetocaloric features of the synthesized materials are investigated by using several techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Magnetic measurements. The XRD and SEM data confirm the co-existence of perovskite and copper oxide phases. The magnetization data unveil that the studied composite exhibits a ferromagnetic to paramagnetic transition close to room-temperature (TC = 295 K). More importantly, its magnetocaloric effect in terms of the entropy change remains similar to that of (La 0.45 Nd 0.25)Sr 0.3 MnO 3 /0.05CuO only synthesized by the conventional solid-state reaction technique. This points out the possibility of upscaling the production of magnetocaloric oxides to industrial levels using the spray-drying technique. [ABSTRACT FROM AUTHOR]