Magnetic self-organized atomic laminate from first principles and thin film synthesis.

The first experimental realization of a magnetic M(n+1)AX(n) (MAX) phase, (Cr(0.75)Mn(0.25))(2)GeC, is presented, synthesized as a heteroepitaxial single crystal thin film, exhibiting excellent structural quality. This self-organized atomic laminate is based on the well-known Cr(2)GeC, with Mn, a new element in MAX phase research, substituting Cr. The compound was predicted using first-principles calculations, from which a variety of magnetic behavior is envisaged, depending on the Mn concentration and Cr/Mn atomic configuration within the sublattice. The analyzed thin films display a magnetic signal at room temperature.

Competing interface and bulk anisotropies in Co-rich TbCo amorphous thin films.

We study the magnetic properties of amorphous TbxCo100-xfilms withxin the range 8-12 at% and with a thickness of 5-100 nm. In this range the magnetic properties are shaped by a competition between a perpendicular bulk magnetic anisotropy and an in-plane interface anisotropy, in addition to the changes in magnetization. This results in a temperature controllable spin reorientation transition from in-plane to out-of-plane which is thickness and composition dependent. Furthermore, we show that perpendicular anisotropy is recovered throughout an entire TbCo/CoAlZr multilayer, where neither TbCo nor CoAlZr single layers exhibit perpendicular anisotropy. This illustrates the important role of the TbCo interfaces in the overall effective anisotropy.

Reversible exchange bias in epitaxial V2O3/Ni hybrid magnetic heterostructures.

In this work we present a temperature and angular dependent study of the structural and magnetic properties in highly crystalline V2O3/Ni/Zr magnetic heterostructure films. Our investigation focuses on the coupling between the ferromagnetic Ni layer and V2O3layer which undergoes an antiferromagnetic/paramagnetic phase transition coupled to the structural phase transition of the material at around 150 K. Structural investigations using x-ray diffraction reveal highly crystalline films of a quality which has previously not been reported in the literature. The Ni layers display an absence of in-plane magnetic anisotropy owing to the highly textured (1 1 1) layering of the Ni films on the underlying V2O3(0 0 0 1) oriented layer. During the transition we observe a strain related enhancement of the coercivity and the onset of a weak exchange bias for cooling under an external magnetic field. Heating the films to above the transition temperature, the exchange bias in the Ni is removed and can be reversed upon subsequent cooling under an inverted external magnetic field. Using temperature dependent polarized neutron reflectometry we investigate the film structure at the interface, capturing the magnetic and nuclear profiles.

Tuneable exchange-spring stiffness in amorphous magnetic trilayer structures.

We investigate the magnetic properties of amorphous Sm10Co90/Co60(Al70Zr30)40/Co85(Al70Zr30)15exchange-spring magnet trilayers. The magnetically soft Co85(Al70Zr30)15layer is coupled to the magnetically hard Sm10Co90layer through the weakly magnetic low-TcCo60(Al70Zr30)40spacer layer. The strength of the coupling can be controlled with temperature and the coupling persists above the intrinsicTcof the spacer layer due to a long-range magnetic proximity effect. Polarized neutron reflectivity is used to examine the magnetic profile of the trilayers during magnetization reversal. A two-step switching occurs, with the switching angle of the soft layer strongly dependent on the strength of the coupling. In the strong coupling regime a magnetic state can be achieved where the soft layer magnetization is perpendicular to the hard layer whereas in the weak coupling regime the soft layer reverses fully.

A magnetron sputtering system for the preparation of patterned thin films and in situ thin film electrical resistance measurements.

We describe a versatile three gun magnetron sputtering system with a custom made sample holder for in situ electrical resistance measurements, both during film growth and ambient changes on film electrical properties. The sample holder allows for the preparation of patterned thin film structures, using up to five different shadow masks without breaking vacuum. We show how the system is used to monitor the electrical resistance of thin metallic films during growth and to study the thermodynamics of hydrogen uptake in metallic thin films. Furthermore, we demonstrate the growth of thin film capacitors, where patterned films are created using shadow masks.