Merőleges anizotrópiájú ötvözetfilmek és a mágneses szerkezet ionsugaras kialakítása = Perpendicular anisotropy multicomponent films and ion beam tailoring of their magnetic structure

A vékonyrétegek szerkezete és mágneses tulajdonságai érzékeny módon összefüggnek. A rétegtulajdonságok módosításának legfontosabb eszköze az ionimplantáció volt. Módosítottuk homogén rétegek fizikai, kémiai, és mágneses tulajdonságait, és ezzel módosítottuk a mágneses multirétegekben a rétegprofilt. Metastabil FePd a lokális környezetektől függő Fe öndiffúziós állandókat határoztunk meg. Kapcsolatot találtunk az ionsugaras keveredés és a diffúziós állandó között. Alkalmazásként periodikus laterális mágneses mintázatot hoztunk létre besugárzással, neutrontükrök feszültségmentesítésére és monokromátor tervezésére alkalmas eljárásokat dolgoztunk ki. | The structure and magnetic properties of thin films are sensitively interrelated. Physical, chemical and consequent magnetic properties of the films and their depth profile were modified in magnetic multilayers promarily by ion implantation. Three Fe self-diffusion coefficients were determined according to the local Fe-environments in metastable FePd films. A relation has been revealed between ion beam mixing rate and diffusion coefficient. As applications of the achived scientific results periodic lateral magnetic pattern was created using ion implantation and developed procedures for strain release of neutron mirrors and monochromator design

Phonon confinement and interface lattice dynamics of ultrathin high-rare earth sesquioxide films: the case of Eu₂O₃ on YSZ(001)

The spatial confinement of atoms at surfaces and interfaces significantly alters the lattice dynamics of thin films, heterostructures and multilayers. Ultrathin films with high dielectric constants (high-k) are of paramount interest for applications as gate layers in current and future integrated circuits. Here we report a lattice dynamics study of high-k Eu$_{2}$O$_{3}$ films with thicknesses of 21.3, 2.2, 1.3, and 0.8 nm deposited on YSZ(001). The Eu-partial phonon density of states (PDOS), obtained from nuclear inelastic scattering, exhibits broadening of the phonon peaks accompanied by up to a four-fold enhancement of the number of low-energy states compared to the ab initio calculated PDOS of a perfect Eu$_{2}$O$_{3}$ crystal. Our analysis demonstrates that while the former effect reflects the reduced phonon lifetimes observed in thin films due to scattering from lattice defects, the latter phenomenon arises from an ultrathin EuO layer formed between the thin Eu$_{2}$O$_{3}$ film and the YSZ(001) substrate. Thus, our work uncovers another potential source of vibrational anomalies in thin films and multilayers, which has to be cautiously considered

A Three-Dimensional Analysis of Magnetic Nanopattern Formation in FeRh Thin Films on MgO Substrates: Implications for Spintronic Devices

Magnetic nanopatterns were successfully created in FeRh thin film deposited on MgO (100) substrates. Silica and polystyrene spherical masks, nominally 500 and 1000 nm in diameter, respectively were applied on the surface of the sample in order to locally shadow the film against the effect of 110 keV energy neon-ion irradiation with fluences of 10 15 and 10 16 ions/ cm2 . Such nanosphere-lithography technique allows for projecting the mask geometry on the magnetic structure of the FeRh film. Conversion-electron Mö ssbauer spectroscopy and magnetic force microscopy were used to determine the ferromagnetic ratio and the magnetic pattern in the samples, and nuclear resonance scattering of synchrotron radiation was applied to obtain the in- depth magnetic profile. From the results obtained, the possible three-dimensional (3D) structure of the created individual magnetic domains was also constructed. Overall, the great customizability of the presented nanosphere-lithography technique in FeRh thin film provides opportunities for developing cutting-edge spintronic applications

Synergy effect of temperature, electric and magnetic field on the depth structure of the FeRh/BaTiO3 composite multiferroic

FeRh based composite multiferroic materials have attracted great scientific interest due to their wide variety of possible applications in future nano device technology. In the recent work, a comprehensive study on the depth dependence of the metamagnetic phase transition in FeRh/BaTiO3 heterostructure is reported by means of single or combined external stimulus such as heat, magnetic or electric field. Grazing-incidence nuclear scattering experiments revealed significant discrepancies in the mechanism of the antiferromagnetic/ferromagnetic reor- dering induced by the different effects, with distinguished role of both upper and lower interfaces

Phonon confinement and spin-phonon coupling in tensile-strained ultrathin EuO films

Reducing the material sizes to the nanometer length scale leads to drastic modifications of the propagating lattice excitations (phonons) and their interactions with electrons and magnons. In EuO, a promising material for spintronic applications in which a giant spin-phonon interaction is present, this might imply a reduction of the degree of spin polarization in thin films. Therefore, a comprehensive investigation of the lattice dynamics and spin-phonon interaction in EuO films is necessary for practical applications. We report a systematic lattice dynamics study of ultrathin EuO(001) films using nuclear inelastic scattering on the Mössbauer-active isotope ^{151}Eu and first-principles theory. The films were epitaxially grown on YAlO_{3}(110), which induces a tensile strain of ca. 2%. By reducing the EuO layer thickness from 8 nm to a sub-monolayer coverage, the Eu-partial phonon density of states (PDOS) reveals a gradual enhancement of the number of low-energy phonon states and simultaneous broadening and suppression of the peaks. These deviations from bulk features lead to significant anomalies in the vibrational thermodynamic and elastic properties calculated from the PDOS. The experimental results, supported by first-principles theory, unveil a reduction of the strength of the spin-phonon interaction in the tensile-strained EuO by a factor of four compared to a strain-free lattice