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Allieta, Mattia; Oliva, Cesare; Scavini, Marco; Cappelli, S.; Pomjakushina, E.; Scagnoli, V.

doi:10.1103/physrevb.84.235144

Cited by 7 publications

(28 citation statements)

References 26 publications

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“…Indeed, we will show that at ≥ 0.5 the ESR pattern assumes the shape of a single Dysonian line. This is not new in the literature and it was found also by us in different systems, like LaMnO 3+ , [13] and GdBaCo 2 O 5+ [10,14]. In those cases, that spectral profile was attributed to the electron mobility.…”

Section: Introductionsupporting

confidence: 66%

Electron Spin Resonance and Atomic Force Microscopy Study on Gadolinium Doped Ceria

Oliva

Orsini

Cappelli

et al. 2015

Journal of Spectroscopy

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A combined electron spin resonance (ESR) and atomic force microscopy (AFM) study on Ce1−xGdxO2−x/2samples is here presented, aimed at investigating the evolution of the ESR spectral shape as a function ofxin a wide composition range. At lowx=0.02, the spectrum is composed of features atgeff≈2; 2.8; 6. With increasingx, this pattern merges into a singlegeff≈2broad ESR curve, which assumes a Dysonian-shaped profile atx≥0.5, whereas, at thesexvalues, AFM measurements show an increasing surface roughness. It is suggested that the last could cause the formation of surface polaritons at the origin of the particular ESR spectral profile observed at these high Gd doping levels.

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Section: Introductionsupporting

confidence: 66%

Electron Spin Resonance and Atomic Force Microscopy Study on Gadolinium Doped Ceria

Oliva

Orsini

Cappelli

et al. 2015

Journal of Spectroscopy

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“…7 In particular, δ affects the mixed valence state of the cobalt ions, resulting in different Co 2+ /Co 3+ and Co 4+ /Co 3+ ratios with cobalt species stabilizing in several spin states. [5][6][7][8][9] In the case of the LnBaCo 2 O 5.0 system (Ln = Y, 5 Tb, 6 Dy, 6 Ho 6 ), where the Co 2+ /Co 3+ ratio equals 1, neutron powder diffraction (NPD) shows the insurgence of both charge and magnetic ordering associated with structural phase transitions. In the high-T paramagnetic (PM) state, these compounds display a tetragonal structure P 4/mmm and an a × a × 2a cell metric, where a is the primitive cubic perovskite lattice parameter [ Fig.…”

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confidence: 99%

Charge ordering transition in GdBaCo2O5: Evidence of reentrant behavior

et al. 2013

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We present a detailed study on the charge ordering transition in a GdBaCo 2 O 5.0 system by combining highresolution synchrotron powder/single-crystal diffraction with electron paramagnetic resonance experiments as a function of temperature. We found a second-order structural phase transition at T CO = 247 K (Pmmm to Pmma) associated with the onset of long-range charge ordering. At T min ≈ 1.2T CO, the electron paramagnetic resonance linewidth rapidly broadens, providing evidence of antiferromagnetic spin fluctuations. This likely indicates that, analogously to manganites, the long-range antiferromagnetic order in GdBaCo 2 O 5.0 sets in at ≈T CO . Pair distribution function analysis of diffraction data revealed signatures of structural inhomogeneities at low temperature. By comparing the average and local bond valences, we found that above T CO the local structure is consistent with a fully random occupation of Co 2+ and Co 3+ in a 1:1 ratio and with a complete charge ordering below T CO . Below T ≈ 100 K the charge localization is partially melted at the local scale, suggesting a reentrant behavior of charge ordering. This result is supported by the weakening of superstructure reflections and the temperature evolution of electron paramagnetic resonance linewidth that is consistent with paramagnetic reentrant behavior reported in the GdBaCo 2 O 5.5 parent compound.

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“…Local atomic fluctuations promote broken symmetry states [3,4], nanoscale phase separations [1,2], and reentrant phase transitions [4] associated with emergent phenomena, such as colossal magnetoresistance (MR) and high-temperature superconductivity [1,2]. Therefore the interplay between the structure and such inhomogeneous phases plays a pivotal role in the understanding the physics of the strongly correlated electron oxides at the microscopic level [3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Layered cobaltite GdBaCo 2 O 5+δ (GBCO) is an ideal system to investigate the role of nanoscale phase separation due to its intrinsic inhomogeneous structure [4][5][6][10][11][12]. Giant MR effects [11], magnetic ordering [12], charge ordering [4], and metal-insulator transition (MIT) [6][7][8][9][10][11][12] coexist within the same material without requiring extrinsic chemical doping. In the optimal oxygen δ range 0.45 δ 0.55, the structure of GBCO consists of layers [CoO 2 ][BaO][CoO 2 ][GdO 0.5 ] stacking along the c axis of the Pmmm space group with a a × 2a × 2a cell metric, where a is the primitive cubic perovskite lattice parameter [6].…”

Section: Introductionmentioning

confidence: 99%

“…Giant MR effects [11], magnetic ordering [12], charge ordering [4], and metal-insulator transition (MIT) [6][7][8][9][10][11][12] coexist within the same material without requiring extrinsic chemical doping. In the optimal oxygen δ range 0.45 δ 0.55, the structure of GBCO consists of layers [CoO 2 ][BaO][CoO 2 ][GdO 0.5 ] stacking along the c axis of the Pmmm space group with a a × 2a × 2a cell metric, where a is the primitive cubic perovskite lattice parameter [6]. In the GdO 0.5 plane the oxygen site 1c (0,0,1/2) is almost empty whereas the oxygen site 1g (0,1/2,1/2) is fully occupied, giving rise to two types of coordination environments for cobalt ions, i.e., * mattia.allieta@gmail.com pyramidal (CoO 5 ) and octahedral (CoO 6 ) [6].…”

Section: Introductionmentioning

confidence: 99%

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Interplay of structural and magnetic nanoscale phase separation in layered cobaltites

et al. 2015

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We report on the structural, electronic, and magnetic phases of a previously unexplored region in the phase diagram of GdBaCo 2 O 5+δ (δ = 0.57 and 0.63). Despite a homogenous average structure displayed by both the samples, the orthorhombic highly oxygenated GdBaCo 2 O 5.63 shows clear signatures of structural nanoscale phase separation. By combining a pair distribution function with photoluminescence and electron spin resonance techniques, we found that the nanoscale phase separation is induced by an inhomogeneous distribution of ferromagnetic Co 3+ − Co 4+ clusters embedded in an antiferromagnetic Co 3+-rich matrix. In addition, we uncovered a phase evolution involving the collapse of the orthorhombic strain below room temperature. The origin of this noncanonical transition seems to be associated with the interplay of the observed nanoscale phase separation and a new magnetic phase transition occurring below T ∼ 180 K.

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Spin-lattice interaction in the insulator-to-metal transition of GdBaCo2O5+δ

Cited by 7 publications

References 26 publications

Electron Spin Resonance and Atomic Force Microscopy Study on Gadolinium Doped Ceria

Electron Spin Resonance and Atomic Force Microscopy Study on Gadolinium Doped Ceria

Charge ordering transition in GdBaCo2O5: Evidence of reentrant behavior

Interplay of structural and magnetic nanoscale phase separation in layered cobaltites

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