Electrical and magnetic properties of (SrMnO3)n∕(LaMnO3)2n superlattices

Adamo, Carolina; Ke, Xianglin; Schiffer, P.; Soukiassian, A.; Warusawithana, Maitri; Maritato, L.; Schlom, D. G.

doi:10.1063/1.2842421

Cited by 86 publications

(94 citation statements)

References 22 publications

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“…Recent work 68,69 on the synthesis of LaMnO 3 thin films in compressive strain on SrTiO 3 substrates has shown indications of a nonbulk ferromagnetic phase which, however, is reported to be insulating, rather than metallic as predicted by our analysis. In our first-principles investigation, there is no evidence for an insulating FM phase for stoichiometric LaMnO 3 .…”

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confidence: 53%

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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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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“…Experiments discovered a surprising insulating ferromagnetic phase in LMO thin films epitaxially grown on the square-lattice SrTiO 3 (STO) substrate [2,[7][8][9][10][11][12][13]. The origin of this puzzling insulating FM phase is unclear.…”

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Intrinsic insulating ferromagnetism in manganese oxide thin films

2014

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“…Focus has been on the case m = 2n corresponding to the average optimal hole doping x = 1/3. 8, 9 The superlattices exhibit a metal-insulator transition as function of temperature for n ≤ 2 and behave as insulators for n ≥ 3. The superlattices undergo a rich variety of transitions among metal, Mott variable range hopping insulator, interaction-induced Efros-Shklovskii insulator, and polaronic insulator.…”

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confidence: 99%

Electron-lattice and strain effects in manganite heterostructures: The case of a single interface

Iorio¹,

Perroni²,

Ramaglia³

et al. 2011

Phys. Rev. B

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A correlated inhomogeneous mean-field approach is proposed in order to study a tight-binding model of the manganite heterostructures (LaM nO3)2n/(SrM nO3)n with average hole doping x = 1/3. Phase diagrams, spectral and optical properties of large heterostructures (up to 48 sites along the growth direction) with a single interface are discussed analyzing the effects of electron-lattice anti-adiabatic fluctuations and strain. The formation of a metallic ferromagnetic interface is quite robust with varying the strength of electron-lattice coupling and strain, though the size of the interface region is strongly dependent on these interactions. The density of states never vanishes at the chemical potential due to the formation of the interface, but it shows a rapid suppression with increasing the electron-lattice coupling. The in-plane and out-of-plane optical conductivities show sharp differences since the in-plane response has metallic features, while the out-of-plane one is characterized by a transfer of spectral weight to high frequency. The in-plane response mainly comes from the region between the two insulating blocks, so that it provides a clear signature of the formation of the metallic ferromagnetic interface.

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Electrical and magnetic properties of (SrMnO3)n∕(LaMnO3)2n superlattices

Cited by 86 publications

References 22 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

Intrinsic insulating ferromagnetism in manganese oxide thin films

Electron-lattice and strain effects in manganite heterostructures: The case of a single interface

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