Uniaxial Strain-Controlled Ground States in Manganite Films

Abstract

Strongly correlated perovskite oxides exhibit a plethera of intriguing phenomena and stimulate a great potential for multifunctional device applications. Utilizing tunable uniaxial strain, rather than biaxial or anisotropic strain, delivered from the crystallography of a single crystal substrate to modify the ground state of strongly correlated perovskite oxides has rarely been addressed for phase-space control. Here, we show that the physical properties of La2/3Ca1/3MnO3 (LCMO) films are remarkably different depending on the crystallographic orientations of the orthorhombic NdGaO3 (NGO) substrates. More importantly, the antiferromagnetic charge-ordered insulating (COI) phase induced in the (100) or (001)-oriented LCMO films can be dramatically promoted (or suppressed) by a uniaxial tensile (or compressive) bending stress along the in-plane [010] direction. By contrast, the COI phase is nearly unaffected along the other transverse in-plane directions. Results from scanning transmission electron microscopy reveal that the (100)- or (001)-oriented LCMO films are uniaxially tensile strained along the [010] direction, while the LCMO/NGO(010) and LCMO/NGO(110) films remaining as a bulklike ferromagnetic metallic state exhibit a different strain state. Density functional theory calculations further reveal that the cooperatively increased Jahn–Teller distortion and charge ordering may be indispensible for the inducing and promoting of the COI phase. These findings provide a path to understand the correlation between local and extended structural distortions imparted by coherent epitaxy and the electronic states for quantum phase engineering.

Evidence of Robust Half-Metallicity in Strained Manganite Films

“…The NGO (001) substrate induces −0.44% (compressive) and +0.57% (tensile) strains, respectively, on the a and b axes of the LCMO orthorhombic unit cell. The consequent lattice distortion , produces important deviations from the bulk properties of LCMO in the “optimal doping” regime (0.3 ≤ x ≤ 0.4), namely a metallic ferromagnet with a well-defined Curie temperature ( T C ) around 240 K . A large hysteresis between the cooling and warming curves of the resistivity is observed for all the thicknesses, as displayed in Figure b–d: the temperature at which the sample makes the transition from insulating to metallic behavior along the decreasing temperature branch ( T 1 ) is lower than the temperature at which the sample makes the opposite transition from metallic to insulating behavior along the increasing temperature branch ( T 2 ).…”

Soliton-Mediated Magnetic Reversal in an All-Oxide-Based Synthetic Antiferromagnetic Superlattice

“…The orthorhombic NGO (001) substrate imposes a tensile strain of +0.85% along the [010] axis and a compressive strain of −0.70% along the [100] axis of the LCMO . This anisotropic strain state can give rise to robust in-plane uniaxial magnetic anisotropy (IMA) along the [010] axis . Thus, we measured all the magnetic properties along the [010] easy axis.…”

Strain-Induced Domain Structure and Its Impact on Magnetic and Transport Properties of Gd0.6Ca0.4MnO3 Thin Films

“… 9 − 12 The structural and physical properties of such materials are strongly dependent on the deposition technique and the lattice mismatch with the substrate, which results in uniaxial strain. 13 − 15 The strain can be responsible for phase separation 16 , 17 and modification of the relation between the lattice parameters in the direction perpendicular to growth ( c ) and the one in the parallel plane ( a ). 18 On the other hand, the fabrication of high-quality perovskite thin films by controlling the strain and the lattice mismatch between the bulk and substrate can affect the electrical and magnetic properties of manganites.…”

“…The mixed-valence A 1– x B x MnO 3 perovskite manganites, where A and B are rare-earth and divalent alkaline elements, have recently become the focus of extensive research due to their unusual magnetic and magnetoresistance properties. − Among the perovskites, the low-bandwidth manganites, such as Pr 1– x Ca x MnO 3 (PCMO) and Gd 1– x Ca x MnO 3 (GCMO), are particularly interesting due to the stable charge ordering (CO) state in the whole doping range, leading to several important features like resistive switching and spin memory effect. − Moreover, the Gd-based low-bandwidth perovskites not only show the CO state near room temperature but also exhibit specific magnetic features, particularly the reversal magnetization at low temperature and in the applied magnetic field, leading to a ferrimagnetic ground state. − The structural and physical properties of such materials are strongly dependent on the deposition technique and the lattice mismatch with the substrate, which results in uniaxial strain. − The strain can be responsible for phase separation , and modification of the relation between the lattice parameters in the direction perpendicular to growth ( c ) and the one in the parallel plane ( a ) . On the other hand, the fabrication of high-quality perovskite thin films by controlling the strain and the lattice mismatch between the bulk and substrate can affect the electrical and magnetic properties of manganites. , …”