Ferromagnetic metallic manganites are employed as prototypical spin injectors in several systems in order to reveal insights in a variety of spin related effects [1,2]. In particular, the La0.7Sr0.3MnO3 (LSMO) compound has stimulated an intense study since, in bulk form, it has one of the highest ferromagnetic transition temperature Tc = 370 K. Understanding and controlling the morpho-structural and magnetic properties of LSMO films as a function of thickness is crucial for realizing applications that commonly demand for ultrathin layers. For this purpose, LSMO films in the thickness range of 4-16 nm were deposited on single-crystal (001) SrTiO3 substrates by means of channel spark ablation [3]. The temperature and angular dependence of the magnetic properties were studied by a vector Vibrating Sample Magnetometer, in conjunction to structural and morphological results. Even the thinnest sample shows ferromagnetism (Tc = 250 K) and Tc enhances with increasing th, reaching a value of about 315 K for th = 16 nm. This gradual approach towards the ferromagnetic properties of bulk LSMO follows a strain driven trend from fully strained films with weakened magnetism towards robust magnetism with a sudden change at about 6 nm. Moreover, with increasing the temperature from 100 K up to 300 K, a change of the magnetic anisotropy from a biaxial to a dominant uniaxial symmetry was clearly observed in all the films. Such a behaviour - probably related to a crossover from a low-temperature regime, where crystalline anisotropy dominates, to a high-temperature one, governed by magnetoelastic anisotropy - occurs progressively, with a substantial isotropic behaviour actually existing in a narrow temperature range.
Structural and magnetic properties of (ultra)thin LaSrMnO films
DEL BIANCO, Lucia;
2015
Abstract
Ferromagnetic metallic manganites are employed as prototypical spin injectors in several systems in order to reveal insights in a variety of spin related effects [1,2]. In particular, the La0.7Sr0.3MnO3 (LSMO) compound has stimulated an intense study since, in bulk form, it has one of the highest ferromagnetic transition temperature Tc = 370 K. Understanding and controlling the morpho-structural and magnetic properties of LSMO films as a function of thickness is crucial for realizing applications that commonly demand for ultrathin layers. For this purpose, LSMO films in the thickness range of 4-16 nm were deposited on single-crystal (001) SrTiO3 substrates by means of channel spark ablation [3]. The temperature and angular dependence of the magnetic properties were studied by a vector Vibrating Sample Magnetometer, in conjunction to structural and morphological results. Even the thinnest sample shows ferromagnetism (Tc = 250 K) and Tc enhances with increasing th, reaching a value of about 315 K for th = 16 nm. This gradual approach towards the ferromagnetic properties of bulk LSMO follows a strain driven trend from fully strained films with weakened magnetism towards robust magnetism with a sudden change at about 6 nm. Moreover, with increasing the temperature from 100 K up to 300 K, a change of the magnetic anisotropy from a biaxial to a dominant uniaxial symmetry was clearly observed in all the films. Such a behaviour - probably related to a crossover from a low-temperature regime, where crystalline anisotropy dominates, to a high-temperature one, governed by magnetoelastic anisotropy - occurs progressively, with a substantial isotropic behaviour actually existing in a narrow temperature range.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
