Enhanced relative cooling power of lanthanum-deficiency manganites La0.77−xMg0.23MnO3 (0 ≤ x ≤ 0.2): structural, magnetic and magnetocaloric properties
“…Due to the rather isotropic nature of MCE, the RCP in the GCFO was estimated as 301 and 309 J/ kg at H//c and H c , respectively, for ΔH = 0–9 T. On the other hand, the RCP in the ECFO was found to be 623 J/kg at H//c and 169 J/kg at H c . The RCP has been estimated in polycrystalline specimens such as La 0.67 Sr 0.22 Ba 0.11 Mn 0.9 Fe 0.1 O 3 55 (241 J/kg for Δ H = 0–5 T), La 0.57 Mg 0.23 MnO 3 56 (176 J/kg for Δ H = 0–5 T), Ni 0.5 Zn 0.5 Fe 2 O 4 57 (161 J/kg for Δ H = 0–2.5 T) and La 0.5 Pr 0.2 Ca 0.1 Sr 0.2 MnO 3 58 (372 J/kg for Δ H = 0–5 T), and in single crystals such as La 0.7 Ca 0.3 MnO 3 59 (358 J/kg for Δ H = 0–5 T), h-DyMnO 3 60 (300 J/kg for Δ H = 0–5 T) and GdScO 3 61 (307 J/kg) for Δ H = 0–7 T). Figure 7 Anisotropic magnetic entropy change in ECFO.…”
Magnetic anisotropy is crucial in examining suitable materials for magnetic functionalities because it affects their magnetic characteristics. In this study, disordered-perovskite RCr0.5Fe0.5O3 (R = Gd, Er) single crystals were synthesized and the influence of magnetic anisotropy and additional ordering of rare-earth moments on cryogenic magnetocaloric properties was investigated. Both GdCr0.5Fe0.5O3 (GCFO) and ErCr0.5Fe0.5O3 (ECFO) crystallize in an orthorhombic Pbnm structure with randomly distributed Cr3+ and Fe3+ ions. In GCFO, the long-range order of Gd3+ moments emerges at a temperature of TGd (the ordering temperature of Gd3+ moments) = 12 K. The relatively isotropic nature of large Gd3+ moment originating from zero orbital angular momentum exhibits giant and virtually isotropic magnetocaloric effect (MCE), with a maximum magnetic entropy change of $$\Delta {S}_{M}$$
Δ
S
M
≈ 50.0 J/kg·K. In ECFO, the highly anisotropic magnetizations result in a large rotating MCE characterized by a rotating magnetic entropy change $$\Delta {S}_{\theta }$$
Δ
S
θ
= 20.8 J/kg·K. These results indicate that a detailed understanding of magnetically anisotropic characteristics is the key for exploring improved functional properties in disordered perovskite oxides.
“…Due to the rather isotropic nature of MCE, the RCP in the GCFO was estimated as 301 and 309 J/ kg at H//c and H c , respectively, for ΔH = 0–9 T. On the other hand, the RCP in the ECFO was found to be 623 J/kg at H//c and 169 J/kg at H c . The RCP has been estimated in polycrystalline specimens such as La 0.67 Sr 0.22 Ba 0.11 Mn 0.9 Fe 0.1 O 3 55 (241 J/kg for Δ H = 0–5 T), La 0.57 Mg 0.23 MnO 3 56 (176 J/kg for Δ H = 0–5 T), Ni 0.5 Zn 0.5 Fe 2 O 4 57 (161 J/kg for Δ H = 0–2.5 T) and La 0.5 Pr 0.2 Ca 0.1 Sr 0.2 MnO 3 58 (372 J/kg for Δ H = 0–5 T), and in single crystals such as La 0.7 Ca 0.3 MnO 3 59 (358 J/kg for Δ H = 0–5 T), h-DyMnO 3 60 (300 J/kg for Δ H = 0–5 T) and GdScO 3 61 (307 J/kg) for Δ H = 0–7 T). Figure 7 Anisotropic magnetic entropy change in ECFO.…”
Magnetic anisotropy is crucial in examining suitable materials for magnetic functionalities because it affects their magnetic characteristics. In this study, disordered-perovskite RCr0.5Fe0.5O3 (R = Gd, Er) single crystals were synthesized and the influence of magnetic anisotropy and additional ordering of rare-earth moments on cryogenic magnetocaloric properties was investigated. Both GdCr0.5Fe0.5O3 (GCFO) and ErCr0.5Fe0.5O3 (ECFO) crystallize in an orthorhombic Pbnm structure with randomly distributed Cr3+ and Fe3+ ions. In GCFO, the long-range order of Gd3+ moments emerges at a temperature of TGd (the ordering temperature of Gd3+ moments) = 12 K. The relatively isotropic nature of large Gd3+ moment originating from zero orbital angular momentum exhibits giant and virtually isotropic magnetocaloric effect (MCE), with a maximum magnetic entropy change of $$\Delta {S}_{M}$$
Δ
S
M
≈ 50.0 J/kg·K. In ECFO, the highly anisotropic magnetizations result in a large rotating MCE characterized by a rotating magnetic entropy change $$\Delta {S}_{\theta }$$
Δ
S
θ
= 20.8 J/kg·K. These results indicate that a detailed understanding of magnetically anisotropic characteristics is the key for exploring improved functional properties in disordered perovskite oxides.
“…Manganese oxides with the perovskite structure are of great interest due to their physical properties which have significant potential for various applications [1][2][3][4][5][6][7][8][9][10]. For decades, steady interest has been focused on manganese compounds with a general formula A 1−x B x MnO 3 , where A is a rare earth element (La, Pr, Sm, Nb), and B, a divalent cation (Ca, Ba, Sr, Pb) [1,2].…”
Section: Introductionmentioning
confidence: 99%
“…The initial interest in these compounds stemmed from the discovery of a colossal magnetoresistance effect [3][4][5][6]. Later, a variety of intriguing magnetic and electrical effects were uncovered in these compounds [7][8][9][10][11][12][13][14][15][16], including the observation of both positive and negative temperature resistance coefficients [17], metal-insulator transitions [18], ferromagnetic-paramagnetic transitions [19,20], and charge ordering [21,22]. These properties make these materials promising for use in magnetic sensors [23], supercapacitors [24], and infrared bolometers [25,26].…”
Complex manganites A1-xCdxMnO3 (A=Pr, La) are synthesized by solid state reaction method. Xray diffraction, scanning electron microscopy, and energy-dispersive analysis are applied to study their crystal structure, surface morphology, elemental and phase composition. X-ray photoelectron spectroscopy (XPS) methods are used to study the charge states of Pr and La cations, as well as to quantify the fractions of coexisting Mn3+ and Mn4+ ions. La3d-, La4d-, Pr4d- и Mn2p-spectra of ions La3+, Pr3+, Mn3+ and Mn4+ are calculated in the isolated–ion approximation with accounting for multiplet splitting and charge transfer effect. Good agreement with the experiment is obtained. The relative fractions of trivalent and tetravalent manganese ions in La0.45Cd0.78Mn0,9O2.86 and Pr0.49Cd0.74Mn0.85O2.91 are determined by fitting the Mn2p spectra by the superpositions of experimental spectra containing only Mn3+ and only Mn4+ ions; they were found to be 0.71Mn3+/0.29Mn4+ and 0.54Mn3+/0.46Mn4+, respectively.
“…Lanthanum manganite (LaMnO 3 ) is one of the most broadly studied systems. 13,14 The ferromagnetic/electric properties of these materials can be achieved by varying the sintering conditions and by doping with various cations on both La and Mn sites. 15,16 In this paper, we have synthesized a set of samples of La 0.5 Sm 0.2 Sr 0.3 Mn (1Àx) Cr x O 3 with different Cr contents and we study its effect of Cr doping on the structural, electrical and dielectric properties of these compounds.…”
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