Shear elastic constant softening in (V1−xCrx)2O3: Second-order nature of the low temperature phase transition

Yang, Haoran; Sladek, R. J.; Harrison, H. R.

doi:10.1016/0038-1098(83)90977-8

Cited by 17 publications

(10 citation statements)

References 10 publications

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“…It was also found that the C 44 elastic constant softens and short-range spin correlation functions abruptly changes at this second order transition in this model. These results are consistent with the ultrasonic-wave measurement 11) and recent neutron scattering experiments.…”

Section: )supporting

confidence: 92%

“…The transition is accompanied by the monoclinic to corundum lattice structure transition and in the ultrasonic wave velocities measurements, the C 44 elastic constant was estimated to soften almost at the transition temperature, showing the nearly second order nature of the transition. 11,12) Contrary to this, in the AFI to PM transition such softening of C 44 is not observed and the transition is of the first order. In the magnetic thermalneutron scattering experiments, abrupt change in short range spin correlation function at the transition temperature was observed.…”

Section: Instead Of Includingmentioning

confidence: 65%

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Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Tanaka

2002

J. Phys. Soc. Jpn.

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The 3d electronic structure and phase transition in pure and Cr doped V2O3 are theoretically investigated in relation to the 3d spin-orbit interaction and lattice distortion. A model consisting of the nearest-neighbor V ion pair with full degeneracy of the 3d orbitals is studied within the many-body point of view. It is shown that each V ion with S = 1 spin state has a large orbital magnetic moment ∼ 0.7µB and no orbital ordering occurs in the antiferromagnetic insulating (AFI) phase. The anomalous resonant Bragg reflection found in the AFI phase is attributed to the magnetic ordering. In the AFI and paramagnetic insulating (PI) phases, Jahn-Teller like lattice instability leads to tilting of the V ion pairs from the corundum c-axis and this causes large difference in the orbital occupation between the paramagnetic metal and the insulating phases, which is consistent with linear dichroic V 2p XAS measurements. To understand the AFI to PI transition, a model spin Hamiltonian is also proposed. The transition is found to be simultaneous order-disorder transition of the magnetic moments and tilting directions of the V ion pairs. Softening of elastic constant C44 and abrupt change in short range spin correlations observed at the transition are also explained.KEYWORDS: V 2 O 3 , electronic structure, phase transition, lattice distortion, orbital ordering, spin-orbit interaction, orbital moment, resonant x-ray scattering, V 2p XAS §1. IntroductionThe metal-insulator (Mott) transition in V 2 O 3 have been extensively studied ever since Mott suggested the possibility of the localization of electrons driven by Coulomb repulsion. 1)Above the transition temperature T N ∼ 155K, the material is paramagnetic metal (PM) and has the corundum structure with the trigonal symmetry (space group R3c). Below T N , it is an antiferromagnetic insulator (AFI) and the lattice distortion to the monoclinic structure (I2/a) takes place.2) Cr doped alloys (V 1−x Cr x ) 2 O 3 exhibit also interesting features. For 0.005 < x < 0.018, at a temperature above the AFI → PM transition, the material further undergoes a PM to paramagnetic insulator (PI) phase transition with no change in the crystal structure. For much higher Cr concentration x > 0.018, the PM phase disappears and a AFI → PI transition takes place.Although V 2 O 3 and its alloys are often referred to a typical example of the Mott-Hubbard system, there are experimental facts showing the complex aspects of these materials, which can not be explained by the simple single-band Hubbard model. In the AFI phase, they exhibit unusual magnetic order, which breaks corundum trigonal symmetry.8) Neutron scattering experiments have been performed by Bao et al. and abrupt change in spatial spin correlation functions has been reported both at the AFI → PM and the AFI → PI transitions. 9, 10)This switching of spin correlation indicates that the phase transitions can not be considered as usual order-disorder magnetic transition. Softening of the C 44 elastic constant has been observed in ultrasonic wa...

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Section: )supporting

confidence: 92%

Section: Instead Of Includingmentioning

confidence: 65%

Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Tanaka

2002

J. Phys. Soc. Jpn.

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“…Phase coexistence thus occurs when τ ∈ [τ r , τ m ], and also the structural transition must take place at τ c within that same interval. At ambient temperature and pressure, τ ∼ c 44 53 eV/cm 3 , which must be greater than τ c since the stable phase is corundum, and c 14 −12.5 eV/cm 3 [63][64][65], so that γ is negative, too. Well below the structural transition at ambient pressure, τ must be smaller than τ r , and γ has to become positive in order for 2 to have the observed values in the monoclinic phase.…”

Section: A Landau-ginzburg Theory Of the Structural Transitionmentioning

confidence: 98%

“…Therefore, upon lowering the temperature T , τ must decrease, while c 14 ∝ γ must increase and cross zero. There are actually evidences, specifically in chromium doped compounds [64], that c 14 does change sign approaching the transition from the corundum phase. We are not aware of any experimental measurement of c 14 in pure V 2 O 3 below room temperature.…”

Section: A Landau-ginzburg Theory Of the Structural Transitionmentioning

confidence: 99%

Nanoscale self-organisation and metastable non-thermal metallicity in Mott insulators

Ronchi,

Franceschini,

De Poli

et al. 2021

Preprint

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“…Therefore, upon lowering the temperature T , τ must decrease, while c 14 ∝ γ must increase and cross zero. There are actually evidences, specifically in chromium doped compounds 63 , that c 14 does change sign approaching the transition from the corundum phase. We are not aware of any experimental measurement of c 14 in pure V 2 O 3 below room temperature.…”

Section: Multiscale Modellingmentioning

confidence: 99%

Nanoscale self-organisation in Mott insulators: a richness in disguise

Ronchi

Franceschini

Poli

et al. 2021

Preprint

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Mott transitions in real materials are first order and almost always associated with lattice distortions, both features promoting the emergence of nanotextured phases. This nanoscale self-organization creates spatially inhomogeneous regions, which can host and protect transient non-thermal electronic and lattice states triggered by light excitation. However, to gain full control of the Mott transition for potential applications in the field of ultrafast switching and neuromorphic computing it is necessary to develop novel spatial and temporal multiscale experimental probes as well as theoretical approaches able to distill the complex microscopic physics into a coarse-grained modelling. Here, we combine time-resolved X-ray microscopy, which snaps phase transformations on picosecond timescales with nanometric resolution, with a Landau-Ginzburg functional approach for calculating the strain and electronic real-space configurations. We investigate V2O3, the archetypal Mott insulator in which nanoscale self-organization already exists in the low-temperature monoclinic phase and strongly affects the transition towards the high-temperature corundum metallic phase. Our joint experimental-theoretical approach uncovers a remarkable out-of-equilibrium phenomenon: the photoinduced stabilisation of the long sought monoclinic metal phase, which is absent at equilibrium and in homogeneous materials, but emerges as a metastable state solely when light excitation is combined with the underlying nanotexture of the monoclinic lattice. Our results provide full comprehension of the nanotexture dynamics across the insulator-to-metal transition, which can be readily extended to many families of Mott insulating materials. The combination of ultrafast light excitation and spatial nanotexture turns out to be key to develop novel control protocols in correlated quantum materials.

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Shear elastic constant softening in (V1−xCrx)2O3: Second-order nature of the low temperature phase transition

Cited by 17 publications

References 10 publications

Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Nanoscale self-organisation and metastable non-thermal metallicity in Mott insulators

Nanoscale self-organisation in Mott insulators: a richness in disguise

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Shear elastic constant softening in (V1−xCrx)2O3: Second-order nature of the low temperature phase transition

Cited by 17 publications

References 10 publications

Electronic Structure and Phase Transition in V2O3: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Electronic Structure and Phase Transition in V2O3: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Nanoscale self-organisation and metastable non-thermal metallicity in Mott insulators

Nanoscale self-organisation in Mott insulators: a richness in disguise

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Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion

Electronic Structure and Phase Transition in V₂O₃: Importance of 3d Spin-Orbit Interaction and Lattice Distortion