M. Riva

Epitaxial La2∕3Sr1∕3MnO3 thin films with metallic behavior above the Curie temperature

Despite its half-metallic character, La2∕3Sr1∕3MnO3 is currently not considered a good candidate for real spin electronic devices due to the dramatic deterioration of its spin polarization at room temperature. Using pulsed-laser deposition, we have grown thin films of La2∕3Sr1∕3MnO3, which display good room-temperature magnetic properties accompanied by a sizable increase of the temperature at which the metal-insulator transition takes place with respect to the Curie temperature. The persistence of the metallic character well above the Curie temperature indicates minor modifications of the electronic structure near the Fermi level, which is responsible for the half-metallicity. These films are good candidates for increasing the operating temperature of devices based on La2∕3Sr1∕3MnO3.

Fe thin films grown on single-crystal and virtual Ge(001) substrates

Thin Fe films have been epitaxially grown at room temperature on standard single-crystal Ge(001) substrates and virtual Ge∕Si(001) substrates. Their structural, magnetic, and electronic properties have been investigated in situ by spin-polarized inverse photoemission, x-ray photoemission spectroscopy, x-ray photoelectron diffraction, low-energy electron diffraction, and magneto-optical Kerr effect. In both cases Fe grows in a layer-by-layer fashion with very low Ge incorporation in the film (less than 3%) and the bcc local structure becomes evident for coverage larger than 5 ML. The onset of ferromagnetism appears definitively at 3 ML, while the coercive field and the spin polarization of unoccupied Fe states increase with thickness up to 30 ML. The overall behavior is very similar in the case of standard and virtual substrates, so the latter can be employed for growing high-quality Fe∕Ge interfaces.

Magnetic anisotropy at the buried CoO/Fe interface

Interfaces between antiferromagnetic CoO and ferromagnetic Fe are typically characterized by the development of Fe oxides. Recently, it was shown that the use of a proper ultra-thin Co buffer layer prevents the formation of Fe oxides [Brambilla et al., Appl. Surf. Sci. 362, 374 (2016)]. In the present work, we investigate the magnetic properties of such an interface, and we find evidence for an in-plane uniaxial magnetic anisotropy, which is characterized by a multijump reversal behavior in the magnetization hysteresis loops. X-ray photoemission spectroscopy and element-sensitive hysteresis loops reveal that the occurrence of such an anisotropy is a phenomenon developing at the very interface.

Magneto-optical investigation of Fe/CoO/Fe(001) trilayers

In this paper, we report on the characterization of the magnetic properties of layered Fe/CoO/Fe(001) magnetic structures by means of Magneto-Optical Kerr Effect. Hysteresis loops were acquired on samples with variable CoO thickness, from 1 nm to 4 nm, and at different temperatures, from 30 K to room temperature. This characterization offers the opportunity of exploiting the differences in the layer-dependent sensitivity of Kerr rotation and Kerr ellipticity in order to disentangle the contribution of the different Fe layers in the hysteresis loops. Moreover, it allows us to give a detailed overview of the magnetic behavior of the trilayers.