Thermally and field-driven spin-state transitions in (Pr1−<i>y</i>Y<i>y</i>)0.7Ca0.3CoO3

Maryško, M.; Jirák, Z.; Knı́žek, K.; Novák, P.; Hejtmánek, J.; Naito, Tomoyuki; Sasaki, Hiroko; Fujishiro, Hiroyuki

doi:10.1063/1.3559485

Cited by 14 publications

(11 citation statements)

References 9 publications

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“…2(a) is that the transition field increases with increasing temperature. It is completely contrary to the shared tendency of the previous reports on spin crossover compounds such as cobalt oxides [Sr 1−x Y x CoO 3 [33], (Pr 1−y Y y ) 0.7 Ca 0.3 CoO 3 [34,35]] and coordinate compounds (Fe[(phen) 2 (NCS) 2 ] [36], [Mn III (taa)] [37]), where the transition fields are observed to decrease with increasing temperature, as schematically shown by the dashed curve in Fig. 2(a).…”

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confidence: 85%

Spin state ordering of strongly correlatingLaCoO3induced at ultrahigh magnetic fields

et al. 2016

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Magnetization measurements of LaCoO 3 have been carried out up to 133 T generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found at B > 100 T and T > T * = 32 ± 5 K which is characterized by its transition field increasing with increasing temperature. At T < T * , the previously reported transition at B ∼ 65 T was observed. Based on the obtained B-T phase diagram and the Clausius-Clapeyron relation, the entropy of the high-field phase at 80 K is found to be smaller for about 1.5 J K −1 mol −1 than that of the low-field phase. We suggest that the observed two high-field phases may originate in different spatial orders of the spin states and possibly other degrees of freedom such as orbitals. An inherent strong correlation of spin states among cobalt sites should have triggered the emergence of the ordered phases in LaCoO 3 at high magnetic fields. PACS numbers: 75.30.Wx, 75.25.Dk, 75.47.Lx, 75.30.Cr Due to the strong correlations between the electrons, the transition metal oxide serves as a vast field hosting rich electronic phases represented by high-temperature superconductivity, colossal magnetoresistance and magnetic-field-induced ferroelectorics [1,2]. Among them, cobalt oxides are unique for their spin state degrees of freedom which not only bring about a magnetic crossover but also a metal-insulator transition (MIT) [3] in the thermal evolution. Perovskite cobalt oxide, LaCoO 3 , has attracted significant attention for more than five decades for its unusual magnetic and transport properties, namely, the crossover from a diamagnet to a Curie paramagnet at 100 K and the transition from a paramagnetic insulator to a paramagnetic metal at 500 K with increasing temperature [4]. Within the ionic picture, possible spin states of Co g , S = 1) is also argued to be stabilized due to the strong hybridization with the O 2p state [5]. Representative ideas describing the spin states of LaCoO 3 in the temperature range above 100 K are (i) the LS-HS mixture state [6][7][8][9][10][11] and (ii) the IS state [5,12,13]. However, they are still controversial. It is notable that recent theoretical studies on the two-orbital Hubbard model have qualitatively reproduced the thermally induced spin crossover and MIT with paramagnetic local moments [14][15][16]. On the other hand, they are inclined to predict the ordering of different spin states which is not found experimentally except for a few studies [17].The validity of the models on spin states should be well judged by their field effects. One can uncover magnetic excited states using high magnetic fields at low temperatures, eliminating the thermal effect. Thermodynamical properties of the magnetic phase can also be revealed by observing its temperature and magnetic field dependence [18,19] and possibly the orbitals are spatially ordered [22,23] and further, the following two magnetization jumps at B > 100 T are predicted by the Ising type SSC model [22]. With the explosive magnetic flux compression techni...

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Spin state ordering of strongly correlatingLaCoO3induced at ultrahigh magnetic fields

et al. 2016

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“…The fits for the ZFC and FCC runs are shown by the broken lines in Fig. 4 21 These DS values are significantly larger than the total entropy change obtained from heat capacity measurements, 0.28 J mol À1 K À1 and 2.2 J mol À1 K À1 for y ¼ 0.0625 and 0.075, respectively. This discrepancy suggests that the magnetic part of the entropy change will be partially compensated by other terms.…”

Section: Resultsmentioning

confidence: 85%

“…19 A small decrease in the spin-crossover temperature was found also in [Fe(2-pic) 3 ]Cl 2 Á EtOH (2-pic ¼ 2-amino-methyl-pyridine), in which the spin-crossover temperature between LS-and HS-Fe 2þ states was suppressed only by approximately 0.2 K at 7 T from 113 K. 20 Similar experiments performed so far on the present (Pr 1Ày Y y ) 0.7 Ca 0.3 CoO 3 (y ¼ 0.075 À 0.15) system showed a comparable variation with the magnetic field. 21 In particular, T SS ¼ T MI ¼ 64:0 K, determined for the y ¼ 0.075 sample from susceptibility measurements at 0.1 T, decreased by 0.35 K in a magnetic field of 7 T. This paper focuses on the y ¼ 0.0625 compound that exhibits pronounced thermal hysteresis during the transition, related most likely to its low critical temperature. The magnetic and electrical properties for high external fields up to 17 T are presented.…”

Section: Introductionmentioning

confidence: 99%

Suppression of the metal-insulator transition by magnetic field in (Pr1−yYy)0.7Ca0.3CoO3 (y = 0.0625)

Naito

Fujishiro

Nishizaki

et al. 2014

Journal of Applied Physics

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The (Pr 1Ày Y y ) 0.7 Ca 0.3 CoO 3 compound (y ¼ 0.0625, T MIÀSS ¼ 40 K), at the lower limit for occurrence of the first-order metal-insulator (MI) and simultaneous spin-state (SS) transitions, has been studied using electrical resistivity and magnetization measurements in magnetic fields up to 17 T. The isothermal experiments demonstrate that the low-temperature insulating phase can be destabilized by an applied field and the metallic phase returns well below the transition temperature T MIÀSS . The reverse process with decreasing field occurs with a significant hysteresis. The temperature scans taken at fixed magnetic fields reveal a parabolic-like decrease in T MIÀSS with increasing field strength and a complete suppression of the MI-SS transition in fields above 9 T. V C 2014 AIP Publishing LLC. [http://dx

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“…In the bulk (Pr 1-x RE y ) 1-x Ca x CoO 3 systems under ambient pressure, which show the simultaneous MI-SS transition, a volume contraction of $1% took place below T MI $ 100 K. 44 The entropy change makes DS $ 5 JÁK À1 Ámol À1 , 45,46 which means that the internal energy of the low-temperature phase is about DSÁT MI $ 500 JÁmol À1 lower, compared with the high-temperature phase. The present PYCCO films are fixed on the substrate and the lattice parameters and the unit cell volume are difficult to change.…”

Section: Discussionmentioning

confidence: 99%

Electrical resistivity anomaly, valence shift of Pr ion, and magnetic behavior in epitaxial (Pr1-yYy)1-xCaxCoO3 thin films under compressive strain

Fujishiro

Noda

Akuzawa

et al. 2017

Journal of Applied Physics

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We have fabricated (Pr 1Ày Y y) 1-x Ca x CoO 3 (PYCCO) epitaxial films with various thicknesses by pulsed laser deposition on the SrLaAlO 4 (SLAO) substrate that applied an in-plane compressive stress to the film, and investigated the temperature dependence of the electrical resistivity, q(T), of the films. An anomalous q(T) upturn with a broad hysteresis could be clearly observed only for the thinnest film (d ¼ 50 nm), and the q(T) anomaly decreased by increasing film thickness, d. The temperature dependence of the X-ray absorption near-edge structure (XANES) spectra at Pr L 2-edge was measured for the films, and the valence states of praseodymium (Pr) ion were determined using the analysis of the XANES spectra. As a result, the average valence of the Pr ion in the d ¼ 50 nm film slightly increases with decreasing temperature from the common value of 3.0þ around room temperature to 3.15þ at 8 K. The valence shift of Pr is thus similar to what was observed on the PYCCO polycrystalline bulks with an abrupt metal-insulator transition, accompanied by a spinstate (SS) transition of Co ions. Furthermore, the low-temperature SQUID measurements evidenced a paramagnetic behavior down to the lowest temperature, which suggests that the dominant part of Co 3þ ions in the film grown on the SLAO substrate tends to be in the low spin state characteristic for the insulating ground state. These results strongly suggest that the anomalous q(T) upturn in the thin films on the SrLaAlO 4 (SLAO) substrate is closely related to the SS transition of Co ions. On the other hand, PYCCO films grown on the LaAlO 3 (LAO) substrate that applied an in-plane tensile stress showed no valence shift of Pr ions and developed a long range ferromagnetic order, which points to a complete suppression of the low-temperature transition. The behaviors of the epitaxial films are discussed in terms of the in-plane stress exerted by different substrates and accumulated elastic energy.

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Thermally and field-driven spin-state transitions in (Pr1−yYy)0.7Ca0.3CoO3

Cited by 14 publications

References 9 publications

Spin state ordering of strongly correlatingLaCoO3induced at ultrahigh magnetic fields

Spin state ordering of strongly correlatingLaCoO3induced at ultrahigh magnetic fields

Suppression of the metal-insulator transition by magnetic field in (Pr1−yYy)0.7Ca0.3CoO3 (y = 0.0625)

Electrical resistivity anomaly, valence shift of Pr ion, and magnetic behavior in epitaxial (Pr1-yYy)1-xCaxCoO3 thin films under compressive strain

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