Effect of Thermal Processing on the Structural and Magnetic Properties of Epitaxial CoFeGe Films.

The structure and magnetic properties of epitaxial Heusler alloy films (CoFeGe) deposited on MgO (100) substrates were investigated. Films of 60 nm thickness were prepared by magnetron co-sputtering at different substrate temperatures (T), and those deposited at room temperature were later annealed at various temperatures (T). X-ray diffraction confirmed (001) [110] CoFeGe || (001) [100] MgO epitaxial growth.

Spin Glass State in Strained LaCaMnO Thin Films.

Epitaxial strain modifies the physical properties of thin films deposited on single-crystal substrates. In a previous work, we demonstrated that in the case of LaCaMnO thin films the strain induced by the substrate can produce the segregation of a non-ferromagnetic layer (NFL) at the top surface of ferromagnetic epitaxial LaCaMnO for a critical value of the tetragonality τ, defined as = | - |, of τ ≈ 0.024.

Direct Epitaxial Growth of Polar HfZrO Films on Corundum.

Single-phase epitaxial HfZrO films with non-centrosymmetric orthorhombic structure have been grown directly on electrode-free corundum (α-AlO) substrates by pulsed laser deposition. A combination of high-resolution X-ray diffraction and X-ray absorption spectroscopy confirms the epitaxial growth of high-quality films belonging to the 2 space group, with [111] out-of-plane orientation. The surface of a 7-nm-thick sample exhibits an atomic step-terrace structure with a corrugation of the order of one atomic layer, as proved by atomic force microscopy.

Strong Crystallographic Influence on Spin Hall Mechanism in PLD-Grown IrO Thin Films.

Spin-to-charge conversion is a central process in the emerging field of spintronics. One of its main applications is the electrical detection of spin currents, and for this, the inverse spin Hall effect (ISHE) has become one of the preferred methods. We studied the thickness dependence of the ISHE in iridium oxide (IrO2) thin films, producing spin currents by means of the spin Seebeck effect in γ-Fe2O3/IrO2 bilayers prepared by pulsed laser deposition (PLD).

Control of Structural and Magnetic Properties of Polycrystalline CoFeGe Films via Deposition and Annealing Temperatures.

Thin polycrystalline CoFeGe films with composition close to stoichiometry have been fabricated using magnetron co-sputtering technique. Effects of substrate temperature (T) and post-deposition annealing (T) on structure, static and dynamic magnetic properties were systematically studied. It is shown that elevated T (T) promote formation of ordered L2 crystal structure.

Relaxation Mechanisms and Strain-Controlled Oxygen Vacancies in Epitaxial SrMnO Films.

SrMnO has a rich epitaxial strain-dependent ferroic phase diagram, in which a variety of magnetic orderings, even ferroelectricity, and thus multiferroicity, are accessible by gradually modifying the strain. Different relaxation processes, though, including the presence of strain-induced oxygen vacancies, can severely curtail the possibility of stabilizing these ferroic phases. Here, we report on a thorough investigation of the strain relaxation mechanisms in SrMnO films grown on several substrates imposing varying degrees of strain from slightly compressive (-0.

Observation of unexpected uniaxial magnetic anisotropy in LaSrMnO films by a BaTiO overlayer in an artificial multiferroic bilayer.

We studied in detail the in-plane magnetic properties of heterostructures based on a ferroelectric BaTiO overlayer deposited on a ferromagnetic LaSrMnO film grown epitaxially on pseudocubic (001)-oriented SrTiO, (LaAlO)(SrTaAlO) and LaAlO substrates. In this configuration, the combination of both functional perovskites constitutes an artificial multiferroic system with potential applications in spintronic devices based on the magnetoelectric effect. LaSrMnO single layers and BaTiO/LaSrMnO bilayers using the pulsed-laser deposition technique.

Polar-Graded Multiferroic SrMnO3 Thin Films.

Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally.

Epitaxial Stabilization of the Perovskite Phase in (Sr(1-x)Ba(x))MnO3 Thin Films.

A novel mechanism of ferroelectricity driven by off-centering magnetic Mn(4+) ions was proposed in (Sr1-xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1-xBax)MnO3 thin films, 0.

Strain-induced coupling of electrical polarization and structural defects in SrMnO3 films.

Local perturbations in complex oxides, such as domain walls, strain and defects, are of interest because they can modify the conduction or the dielectric and magnetic response, and can even promote phase transitions. Here, we show that the interaction between different types of local perturbations in oxide thin films is an additional source of functionality. Taking SrMnO3 as a model system, we use nonlinear optics to verify the theoretical prediction that strain induces a polar phase, and apply density functional theory to show that strain simultaneously increases the concentration of oxygen vacancies.

Observation of the strain induced magnetic phase segregation in manganite thin films.

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La(2/3)Ca(1/3)MnO(3) (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature.

Enhanced magnetotransport in nanopatterned manganite nanowires.

We have combined optical and focused ion beam lithographies to produce large aspect-ratio (length-to-width >300) single-crystal nanowires of La2/3Ca1/3MnO3 that preserve their functional properties. Remarkably, an enhanced magnetoresistance value of 34% in an applied magnetic field of 0.1 T in the narrowest 150 nm nanowire is obtained.