arXiv subjects

L. Horák

Publications and source records attributed to L. Horák.

5 recordsLinked to original sources

arXiv2025

Single-crystalline CrSb(0001) thin films grown by dc magnetron co-sputtering

The recent discovery of altermagnetism has sparked renewed interest in the growth of epitaxial films of the NiAs-phase polymorph of CrSb. This paper describes the magnetron sputtering-based fabrication and characterization of high-quality single crystalline CrSb(0001) thin films supported by an isostructural nonmagnetic PtSb buffer. X-ray diffraction and scanning transmission electron microscopy show that the films are phase pure and possess a very high crystalline quality (mosaicity ~0.05deg), while also being free of extended crystallographic defects. Both scanning electron microscopy and atomic force microscopy confirm their smooth and homogeneous topography. Additionally, the elemental composition of our films was found to be close to stoichiometric via electron probe microanalysis and x-ray fluorescence. Thus, the developed samples represent an ideal platform for further investigation of the material properties of CrSb.

cond-mat.mtrl-sci↗

arXiv2024

Simulation of ion demixing in halide perovskites using Cahn-Hilliard equation

Light-induced ion demixing in mixed-halide perovskites is simulated numerically using the phenomenological Cahn-Hilliard equation. In the model we consider the energy of local elastic deformation as well as the contribution of free carriers, assuming both the polaron and the bandgap-fluctuation models. The simulation shows that elastic deformation suppresses the demixing while free carriers promote it, however both effects lead to different ion distributions. The free-carrier-induced demixing appears only for larger starting random fluctuations of the ion concentration.

cond-mat.mtrl-sci↗

arXiv2021

Anomalous Magnetoresistance by Breaking Ice Rule in Bi2Ir2O7/Dy2Ti2O7 Heterostructure

While geometrically frustrated quantum magnets are known for a variety of exotic spin states that are of great interests of understanding emergent phenomena as well as enabling revolutionary quantum technologies, most of them are necessarily good insulators which are difficult to be integrated with modern electrical circuit that relies on moving charge carriers. The grand challenge of converting fluctuations and excitations of frustrated moments into electronic responses is finding ways to introduce charge carriers that interact with the localized spins without destroying the spin states. Here, we show that, by designing a Bi2Ir2O7/Dy2Ti2O7 heterostructure, the breaking of the spin ice rule in insulating Dy2Ti2O7 can lead to a charge response in the Bi2Ir2O7 conducting layer that can be detected as anomalous magnetoresistance. These results demonstrate a novel and feasible interfacial approach for electronically probing exotic spin states in insulating magnets, laying out a blueprint for the metallization of frustrated quantum magnets.

cond-mat.str-el↗

arXiv2011

Diffusion of Mn interstitials in (Ga,Mn)As epitaxial layers

Magnetic properties of thin (Ga,Mn)As layers improve during annealing by out-diffusion of interstitial Mn ions to a free surface. Out-diffused Mn atoms participate in the growth of a Mn-rich surface layer and a saturation of this layer causes an inhibition of the out-diffusion. We combine high-resolution x-ray diffraction with x-ray absorption spectroscopy and a numerical solution of the diffusion problem for the study of the out-diffusion of Mn interstitials during a sequence of annealing steps. Our data demonstrate that the out-diffusion of the interstitials is substantially affected by the internal electric field caused by an inhomogeneous distribution of charges in the (Ga,Mn)As layer.

cond-mat.mtrl-sci↗

arXiv2010

Strain control of magnetic anisotropy in (Ga,Mn)As microbars

We present an experimental and theoretical study of magnetocrystalline anisotropies in arrays of bars patterned lithographically into (Ga,Mn)As epilayers grown under compressive lattice strain. Structural properties of the (Ga,Mn)As microbars are investigated by high-resolution X-ray diffraction measurements. The experimental data, showing strong strain relaxation effects, are in good agreement with finite element simulations. SQUID magnetization measurements are performed to study the control of magnetic anisotropy in (Ga,Mn)As by the lithographically induced strain relaxation of the microbars. Microscopic theoretical modeling of the anisotropy is performed based on the mean-field kinetic-exchange model of the ferromagnetic spin-orbit coupled band structure of (Ga,Mn)As. Based on the overall agreement between experimental data and theoretical modeling we conclude that the micropatterning induced anisotropies are of the magnetocrystalline, spin-orbit coupling origin.

cond-mat.mtrl-sci↗