Investigation of Magnetic Processes of Structure-Degraded Ferromagnetic Materials

Katedra fyziky kondenzovaných látekDepartment of Condensed Matter PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Barkhausen noise testing of surface decarburization of steel

Magnetic Barkhausen noise technique was tested for applicability of non-destructive charaterization of the decarburized layer depth. A newly introduced parameter, Barkhausen noise coercivity, was proposed for practical use due to its sensitivity to the tested decarburization and its stability to the measurement conditions

Investigation of Magnetic Processes of Structure-Degraded Ferromagnetic Materials

Katedra fyziky kondenzovaných látekDepartment of Condensed Matter PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Structural and magnetic properties of (NdBa)MnO3 films on lattice-matched substrates

Structural and magnetic properties of (NdBa)MnO3 thin films grown on several perovskite substrates by pulsed laser deposition are presented. A high crystal quality epitaxial film with smooth surface and low level of internal strain may be grown up to thicknesses of 70 nm. The in-plane distortion of the film lattice by the substrate-introduced compressive strain promotes corresponding changes in the out-of-plane lattice constant, following the volume-preserving dilation. The films under tensile strain are growing totally relaxed. Different oxygenation conditions during depositions induce correlated changes of structural and magnetic properties of the material. The temperature of ferromagnetic transition of the films is around 100 K and increases with expansion of the unit cell. The magnetic moment in saturation is usually higher along the longest lattice constant of the film. An increase of the bi-axial compressive strain introduced by the substrate results in a rapid increase of the magnetic moment of the films. The observed effects may be explained by a high level of local distortions due to difference in the ionic radii of Nd and Ba