In magnetism, a domain wall is an interface separating magnetic domains, i.e. areas where magnetization is homogeneous. Domain wall is a transition area between different magnetic moments and usually undergoes an angular displacement of 90 or 180 degrees (Wikipedia).

Apart from magnetic field, domain walls can be moved by spin current. Current-induced domain wall dynamics is an important effect for spintronic applications. The best known concept of domain-wall-based magnetic memory is the racetrack memory (Wikipedia).

Involved researchers

• RNDr. Pavel Baláž, Ph.D.

Magnetism is a class of physical phenomena that are mediated by magnetic fields (Wikipedia).

A large part of the research in our group is focused on study of magnetic materials, especially ferromagnets and antiferromagnetis. Both types of materials are important for spintronics since some of them can be used for generation of spin currents and/or their magnetic moment can be manipulated by spin currents.

Involved researchers

• RNDr. David Wagenknecht, Ph.D.
• Doc. RNDr. Ilja Turek, DrSc.
• Doc. RNDr. Martin Diviš, CSc.
• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.

Magnetization dynamics is extensively studied in physics due to its importance for magnetic memories, data processing, and field sensors. In solid state, magnetic degrees of freedom are influenced by various phenomena to some extent. Thus, apart from magnetic fields, magnetic moments can be manipulated by spin-polarized current, thermal fluctuations, temperature gradients, laser pulses and spin-orbit torques. Importantly, mutual interactions between magnetic moments via exchange coupling and magnetostatic fields becomes important in larger structures and diluted magnetic systems with disorder.

Involved researchers

• RNDr. Pavel Baláž, Ph.D.

Multiferroics are defined as materials that exhibit more than one of the primary ferroic order parameters, ferromagnetism, ferroelectricity, or ferroelasticity in the same phase (Wikipedia).

In our group we focus on multilayer systems consisted of ferroelectric and ferromagnetic layers. It has been shown, that the adjacent ferroelectric layer can modify magnetic anisotropy in the ferromagnetic layer. Thus the magnetic moments can be manipulated by spin current as well as by electric field applied to the ferroelectric part.

Involved researchers

• RNDr. Pavel Baláž, Ph.D.

When electric current passes through a magnetic conductor, the electron flux becomes spin-polarized. We talk about spin current or spin-polarized current. Apart from electric charge, spin current transfer also momentum. This momentum transfer can be observed eg. in magnetic multilayers with noncollinear magnetizations, where spin transfer torques, trasfered by the spin current, act on the localized magnetic moments.

Today, number of different methods of spin current generations are known: spin filtering, spin Seebeck effect, spin Hall effect, spin pumping, or ultrafast laser-induced demagnetization.

Involved researchers

• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.

Spin-transfer torque is an effect in which the orientation of a magnetic layer in a magnetic tunnel junction or spin valve can be modified using a spin-polarized current (Wikipedia).

The effect of spin transfer torque is extensively studied in spintronics due to its potential for magnetic random access memories and data processing. Apart from the magnetic multilayers, spin transfer torque appears also in magnetic thin films with nonhomogeneous magnetization textures and can be used to manipulate with magnetic domain walls, vortices, or skyrmions.

Involved researchers

• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.

A spin valve is a device, consisting of two or more conducting magnetic materials, whose electrical resistance can change between two values depending on the relative alignment of the magnetisations in the layers. The resistance change is a result of so called giant magnetoresistive effect (Wikipedia).

When current density flowing through a spin valve is large enought, it exerts spin transfer torque on the magnetizations, which can lead to magnetization dynamics and magnetization switching.

Involved researchers

• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.

Spin waves are propagating disturbances in the ordering of magnetic materials. These low-lying collective excitations occur in magnetic lattices with continuous symmetry. From the equivalent quasiparticle point of view, spin waves are known as magnons, which are boson modes of the spin lattice (Wikipedia).

In our group we study spin waves and their potential utilization in spintronics. Using analytical and numerical methods we study, how spin waves can be generated by means of spin current, laser pulses, and domain wall dynamics.

Involved researchers

• Doc. RNDr. Ilja Turek, DrSc.
• RNDr. Pavel Baláž, Ph.D.

Spin–orbit interaction (a.k.a. spin–orbit coupling) is a relativistic interaction of a particle's spin with its motion inside a potential. In solid state, spin-orbit interaction can be understood as a momentum-dependent magnetic field acting on the spin of the electron. As a result, when electric current flows through a single magnetic layer, spin-orbit interaction can generate torques, known as spin-orbit torques acting on the localized magnetic moments.

In many magnetic systems lacking bulk or structure inversion symmetry spin-orbit torques substantially influence magnetization dynamics. In some systems, spin-orbit torques can lead to magnetization switching.

Involved researchers

• RNDr. Pavel Baláž, Ph.D.

Spintronics, also known as spin electronics, is the scope of physics which study the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices. In the last decades, spintronics is one of the most developing area in solid state physics connecting physics with material science and engineering.

Involved researchers

• RNDr. David Wagenknecht, Ph.D.
• Doc. RNDr. Ilja Turek, DrSc.
• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.

In 1996 Beaurepaire et al. have shown that a laser pulse can induced a significant reduction of magnetization of a Nickel thin film, which occur in less than a picosecond (Phys. Rev. Lett. 76, 4250). This observation demonstrated that one can manipulate with magnetization in ultrafast way, which is very promising for the future evolution of magnetic memories and data processing.

In our group we study this effect by ab initio calculations as well as by various phenomenological models. We focus mainly on ultrafast demagnetization due to superdiffusive spin transport of hot electrons excited by the laser pulse (Phys. Rev. Lett. 105, 027203).

Involved researchers

• Doc. RNDr. Karel Carva, Ph.D.
• RNDr. Pavel Baláž, Ph.D.