Melting of the cooperative Jahn-Teller distortion in LaMnO 3 single crystal studied by Raman spectroscopy

Martı́n-Carrón, L.; Andrés, A. de

doi:10.1007/pl00011129

Cited by 75 publications

(48 citation statements)

References 15 publications

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“…Consistent with experiment 8,26,47 and previous first-principles results, 16 we find this to be the ground state, with good agreement for the structural parameters and other properties, including the magnitude of the Jahn-Teller distortions, the oxygen octahedron rotation angles, the local magnetic moment of Mn, the exchange coupling, and the direct band gap. The indirect gap (0.83 eV) involves a conductionband minimum at and valence-band maximum near R. This value is close to the previous theoretical result (0.90 eV), 16 though substantially higher than the experimental value (0.24 eV) extracted from transport measurements.…”

supporting

confidence: 89%

“…[1][2][3][4] As a result, there have been many experimental [5][6][7][8] and theoretical [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] studies of the end-member compound LaMnO 3 (LaMnO 3 ). The observed sequence of phases with decreasing temperature is as follows: 8,26 At very high temperature (above 1010 K), LaMnO 3 has a rhombohedral R3c structure, produced by rotation of the oxygen octahedron network of the ideal perovskite structure. From 1010 K down to 750 K, it has an orthorhombic P bnm structure produced by a different pattern of octahedral rotations.…”

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confidence: 99%

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Strong coupling of Jahn-Teller distortion to oxygen-octahedron rotation and functional properties in epitaxially strained orthorhombic LaMnO3

et al. 2013

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First-principles calculations reveal a large cooperative coupling of Jahn-Teller (JT) distortion to oxygenoctahedron rotations in perovskite LaMnO 3 . The combination of the two distortions is responsible for stabilizing the strongly orthorhombic A-AFM insulating (I ) eP bnm ground state relative to a metallic ferromagnetic (FM-M) phase. However, epitaxial strain due to coherent matching to a crystalline substrate can change the relative stability of the two states. In particular, coherent matching to a square-lattice substrate favors the less orthorhombic FM-M phase, with the A-AFM phase stabilized at higher values of tensile epitaxial strain due to its larger volume per formula unit, resulting in a coupled magnetic and metal-insulator transition at a critical strain close to 1%. At the phase boundary, a very large magnetoresistance is expected. Tensile epitaxial strain enhances the JT distortion and opens the band gap in the A-AFM-I c-eP bnm phase, offering the opportunity for band-gap engineering. Compressive epitaxial strain induces a transition within the FM-M phase from the c-eP bnm orientation to the ab-eP bnm orientation with a change in the direction of the magnetic easy axis relative to the substrate, yielding strain-controlled magnetization at the phase boundary. Similar behavior is expected in other JT active P bnm perovskites. (La,M)MnO 3 (M = Ca, Pr, Sr, Ba) has been of great interest due to the couplings among structure, magnetic and orbital orderings, and the resulting functional properties, such as colossal magneto-resistance (CMR). 1-4 As a result, there have been many experimental 5-8 and theoretical 9-25 studies of the end-member compound LaMnO 3 (LaMnO 3 ). The observed sequence of phases with decreasing temperature is as follows: 8,26 At very high temperature (above 1010 K), LaMnO 3 has a rhombohedral R3c structure, produced by rotation of the oxygen octahedron network of the ideal perovskite structure. From 1010 K down to 750 K, it has an orthorhombic P bnm structure produced by a different pattern of octahedral rotations. At 750 K, an orbital-order transition occurs by a cooperative Jahn-Teller transition; 27 however, this distortion does not break the symmetry of the P bnm structure. Finally, a magnetic transition to an A-type antiferromagnetic (A-AFM) ordering (ferromagnetic alignment in the xy planes, with spin direction alternating from plane to plane) occurs at 135 K.It proves to be challenging to reproduce the observed A-AFM ground state of LaMnO 3 , with its half filled e g level, from first principles. If the structural parameters are fixed to the experimental values, the correct magnetic ordering is obtained with a range of density-functional-theory (DFT) methods. However, full optimization of the structure within DFT generally gives a competing FM-M phase as the ground state, 11,17 and the correct ground state is obtained only in calculations with both a generalized gradient form of the density functional and inclusion of a Hubbard U . 16 More generally, various couplings in com...

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confidence: 89%

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confidence: 99%

Strong coupling of Jahn-Teller distortion to oxygen-octahedron rotation and functional properties in epitaxially strained orthorhombic LaMnO3

et al. 2013

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“…As the deduced value, τ c0 = 1.2(2) · 10 −12 sec, is too large to describe a vibrating MnO 6 octahedron [7,8], we speculate that some collective modes of adjacent octahedra [9,10] are responsible for the Mn spin slow fluctuations below and above T JT . To date we are not able to specify all the parameters of these modes.…”

Section: −1mentioning

confidence: 81%

“…Unfortunately, to date experimental structural information on OO [4,[7][8][9][10] has not much electronic counterpart. The OO provides a remarkable anisotropy of the effective exchange interaction [2], which explains the A-type antiferromagnetic (AF) spin order below T N ∼ 140 K [11,12].…”

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confidence: 99%

Melting of the orbital order in LaMnO3probed by NMR

et al. 2013

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The Mn spin correlations were studied near the O -O phase transition at TJT = 750 K, up to 950 K with 17 O and 139 La NMR in a stoichiometric LaMnO3 crystalline sample. The measured local hyperfine fields originate from the electron density transfered from the e g -and t 2g -orbitals to the 2s(O) and 6s(La) orbits, respectively. By probing the oxygen nuclei, we show that the correlations of the Mn spins are ferromagnetic in the ab-plane and robust up to TJT whereas along the c-axis, they are antiferromagnetic and start to melt below TJT , at about 550 K. Above TJT the ferromagnetic Mn-Mn exchange interaction is found isotropic. The room temperature orbital mixing angle, ϕnmr = 109 ± 1.5• , of the e g ground state is close to the reported value which was deduced from structural data on Jahn-Teller distorted MnO6 octahedra. For T > TJT LaMnO3 can be described in terms of non-polarized eg-orbitals since both eg-orbitals are equally occupied.

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“…5B 2g ? 5B 3g ) [11][12][13]. These modes can be classified into two symmetric and four antisymmetric stretching modes, four bending modes and six rotation and tilt modes of the octahedra.…”

Section: Resultsmentioning

confidence: 99%

Perovskite La1−x Sr x Ga1−y Mn y O3 solid solution crystals: Raman spectroscopy characterization

Runka

Berkowski

2012

J Mater Sci

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The first-order orthorhombic-rhombohedral phase transition of La 1-x Sr x Ga 1-y Mn y O 3 (LSGMn) crystals is studied by Raman spectroscopy. An increase in Mn content causes significant changes in Raman spectra, especially in the high-wavenumber spectral range. The Raman spectrum of La 1-x Sr x Ga 1-y Mn y O 3 compound with x = y = 0.02 is dominated by MnO 6 internal vibrations. Moreover, a change in the spectrum of this crystal is observed when the 785-nm excitation line is used. Essential reduction in the number of Raman modes during the phase transition is experimentally observed. The temperature of the phase transition decreases with increasing Sr and Mn contents, at the rate of about 20 K/at%.

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Melting of the cooperative Jahn-Teller distortion in LaMnO 3 single crystal studied by Raman spectroscopy

Abstract: PACS. 63.20.-e Phonons in crystal lattices – 75.30.Vn Colossal magnetoresistance,

Cited by 75 publications

References 15 publications

Strong coupling of Jahn-Teller distortion to oxygen-octahedron rotation and functional properties in epitaxially strained orthorhombic LaMnO3

Strong coupling of Jahn-Teller distortion to oxygen-octahedron rotation and functional properties in epitaxially strained orthorhombic LaMnO3

Melting of the orbital order in LaMnO3probed by NMR

Perovskite La1−x Sr x Ga1−y Mn y O3 solid solution crystals: Raman spectroscopy characterization

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