Magnetic tunnel junction is a multilayer structure consisted of two ferromagnets separated by a thin insulator. If the insulating layer is thin enough (typically a few nanometers), electrons can tunnel from one ferromagnet into the other. The resistance of magnetic tunnel junction is generally dependent on the relative magnetic configuration of the ferromagnetic layers. This phenomena is known as tunnel magnetoresistance (TMR).

Involved researchers

• RNDr. Karel Carva, 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.
• RNDr. Karel Carva, Ph.D.
• 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

• 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

• 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

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

Tunnel magnetoresistance (TMR) is a magnetoresistive effect that occurs in a magnetic tunnel junction, which is a component consisting of two ferromagnets separated by a thin insulator (). In such structures, the total electric resistance generally depends on the relative magnetic configuration of the magnetic layers.

Involved researchers

• RNDr. Karel Carva, 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

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