Structural and Magnetic Properties of Spinel FeV<sub>2</sub>O<sub>4</sub>with Two Ions Having Orbital Degrees of Freedom

Katsufuji, T.; Suzuki, Takehito; Takei, H.; Shingu, M.; Kato, Kenichi; Osaka, Keiichi; Takata, Masaki; Sagayama, Hajime; Arima, T.

doi:10.1143/jpsj.77.053708

Cited by 95 publications

(95 citation statements)

References 18 publications

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“…This sample also shows no OO transition due to the fact that it is approaching the itinerant electron behavior with the small V-V distance. In the AV 2 O 4 system, this increased electronic itinerancy due to the decreased V-V distance has been theoretically predicted [22,23] and experimentally confirmed [24][25][26]; (iii) FeV 2 O 4 [27][28][29][30][31][32] exhibits at least three transitions. It is unique since the Fe 2+ (3d 6 ) ions have orbital degrees of freedom in the doubly degenerate e g states.…”

Section: Introductionmentioning

confidence: 72%

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Sinclair

Cao

et al. 2015

Phys. Rev. B

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The magnetic and structural properties of single crystal Fe1−xCoxV2O4 samples have been investigated by performing specific heat, susceptibility, neutron diffraction, and X-ray diffraction measurements. As the orbital-active Fe 2+ ions with larger ionic size are gradually substituted by the orbital-inactive Co 2+ ions with smaller ionic size, the system approaches the itinerant electron limit with decreasing V-V distance. Then, various factors such as the Jahn-Teller distortion and the spin-orbital coupling of the Fe 2+ ions on the A sites and the orbital ordering and electronic itinerancy of the V 3+ ions on the B sites compete with each other to produce a complex magnetic and structural phase diagram. This phase diagram is compared to those of Fe1−xMnxV2O4 and Mn1−xCoxV2O4 to emphasize several distinct features.

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Section: Introductionmentioning

confidence: 72%

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Sinclair

Cao

et al. 2015

Phys. Rev. B

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“…For x = 0, transition temperatures are referred by the previous report [4]. The structural transition temperature T s decreases rapidly as the Mn 2+ concentration increases, and then for x ≥ 0.2, this structural phase transition disappears.…”

Section: Resultsmentioning

confidence: 85%

“…On the other hand, the FM transition temperature T N1 , which corresponds to We discuss the origin of the phase transitions for x = 0.1 and 0.2. From the previous studies on FeV 2 O 4 [4,6], lattice distortion at T s is derived from cooperative JT effect of Fe 2+ ions, where two of three e orbital electrons occupy 3z 2 -r 2 orbital with lower energy. Therefore, FeO 4 tetrahedron is compressed along c-axis.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, vanadium spinels AV 2 O 4 , where the divalent A 2+ (A = Mn, Fe, Co, Zn, Mg, and Cd) and the trivalent V 3+ ions occupy the tetrahedral (A-site) and the octahedral (B-site) sites in a normal spinel structure, respectively, have been studied intensively because of the variety of interesting phenomena related with orbital degrees of freedom because the V 3+ ions have 3d 2 configurations in the triply degenerate t 2g level [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…This compound exhibits the successive structural phase transitions from a cubic to a tetragonal phase (tetraHT; c < a) at T s = 140 K, from a tetraHT to an orthorhombic (ortho) phase at 110 K, and from an orthorhombic to another tetragonal phase (tetraLT; c > a) at 60 K [4]. Whereas, ferrimagnetic (FM) transition with the Fe 2+ and V 3+ moments anti-aligned at T N1 = 110 K and non-collinear ferrimagnetic (NFM) transitions at T N2 = 60 K was reported [5].…”

Section: Introductionmentioning

confidence: 99%

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Structural and Magnetic Properties in Spinel Oxide Fe₁₋_xMn_xV₂O₄

Kawaguchi¹,

Ishibashi²,

Miki³

et al. 2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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Structural properties in spinel oxide Fe 1−x Mn x V 2 O 4 for x ≤ 0.4 have been studied using synchrotron powder diffraction experiments. The successive structural phase transitions similar to those observed in FeV 2 O 4 are observed for x = 0.1. Whereas, the only lattice distortion of cubic-to-tetragonal (c > a) is observed for x = 0.3 and 0.4. Furthermore, we have also measured the magnetization and heat capacity. The results indicate that the temperatures of magnetic phase transitions at ferrimagnetic and non-collinear ferrimagnetic order for x ≤ 0.2 correspond to those of structural transitions of orthorhombic and tetragonal (c > a), respectively. On the other hand, the temperatures of ferrimagnetic phase transition for x = 0.3 and 0.4 are consistent with those of structural transition of a cubic-totetragonal phase (c > a). These results are discussed in terms of orbital state of Fe 2+ and V 3+ ions considering the Jahn-Teller effects and spin-orbit coupling.

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Magnetocaloric Materials with Multiple Instabilities

2017

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the cases of H = 0 and H ≠ 0. In the zero field, the entropy exhibits an anomaly at a ferromagnetic (or ferrimagnetic) transition temperature (T C ), where the slope changes. As a magnetic field is applied to the material at around T C , the fluctuation is suppressed and the entropy is reduced. By exploiting this effect and combining several processes to form a thermodynamic cycle, e.g., Brayton cycle (i)→(ii)→(iii)→(iv)→(i), [7] heat can be extracted from the magnetic material to the thermal bath.While there are several prerequisites (e.g., magnetic and thermal hysteresis properties, mechanical stability, etc.) for materials to be applied to magnetic refrigeration, the enhanced magnitude of the magnetocaloric effect is of primary importance. The magnitude of the magnetocaloric effect is usually evaluated as the isothermal entropy change ΔS = S(H, T) -S(H = 0, T), or adiabatic temperature change ΔT, which are illustrated in Figure 1a, for a given magnetic field change ΔH. In many cases, the isothermal entropy change ΔS is adopted to argue the magnetocaloric effect as it is easier to experimentally evaluate than the adiabatic temperature change ΔT. Here, ΔS is calculated from a series of MH curves with a fine temperature interval using the Maxwell relationRecent research on magnetocaloric materials has focused on first-order magnetic transition systems, rather than secondorder ones because of the enhanced magnitude of the magnetocaloric effect in the former class of materials. [1] In second-order transition systems, the entropy value itself is continuous as a function of temperature, and only its temperature derivative is discontinuous, as shown in the upper panel of Figure 1b. Thus, the entropy change -ΔS displays a triangular-like shape with broad tails at both the high-and low-temperature sides. In this case, the maximum value of -ΔS is generally not very large. On the other hand, in the case of the first-order transition, the entropy itself changes discontinuously at the transition temperature, and therefore, the isothermal entropy change -ΔS tends to be large in magnitude for a rather narrow range of temperatures, as illustrated in Figure 1c. At the same time, the temperature profile of -ΔS indicates a rectangular-like shape rather than the triangular shape in the case of the secondorder transition. Based on these arguments, first-order transition systems have more widely been investigated than secondorder transition systems. Representative examples showing the The magnetocaloric effect is a well-known phenomenon where the temperature of a magnetic material varies upon application or removal of a magnetic field. This effect is anticipated to be applied to magnetic refrigeration technology, which is environmentally benign. For practical applications, it is essential to explore and expand the materials horizon of novel magnets that exhibit giant magnetocaloric effects to achieve sufficient cooling efficiency. In this article, several attempts to enhance the magnetocaloric effect are reviewed from the viewpoint...

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Structural and Magnetic Properties of Spinel FeV₂O₄with Two Ions Having Orbital Degrees of Freedom

Cited by 95 publications

References 18 publications

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Structural and Magnetic Properties in Spinel Oxide Fe₁₋_xMn_xV₂O₄

Magnetocaloric Materials with Multiple Instabilities

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Structural and Magnetic Properties of Spinel FeV2O4with Two Ions Having Orbital Degrees of Freedom

Cited by 95 publications

References 18 publications

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Structural and Magnetic Properties in Spinel Oxide Fe1−xMnxV2O4

Magnetocaloric Materials with Multiple Instabilities

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Structural and Magnetic Properties of Spinel FeV₂O₄with Two Ions Having Orbital Degrees of Freedom

Structural and Magnetic Properties in Spinel Oxide Fe₁₋_xMn_xV₂O₄