This research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 ‘National Excellence Program’.

There are some equipments, that are quite useful in everday research, but they are difficult to purchase on a grant budget. The most convenient solution to this problem is to put them on the Christmas wishlist.

In solid state physics experiment you need some samples to study, in our case crystals. With this crystal growing kit it is possible to grow your own crystals in various colours dedicated to optical experiments.

A powerful light source for the optical experiments could be this high-tech laser saber. It can be built at home as well and can also be used for recreational purposes.

When modeling the crystal structure of studied materials this magnetic construction set can come in quite handy. Or one of the magnets can be used to build a simple homopolar motor.

To be able to interpret the experimental data one also needs to check other people’s results in the literature.

This research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 ‘National Excellence Program’.

When a photon with a given energy is absorbed (its energy is propertional to the light frequency), it causes a transition of the system between two energy levels of an energy difference corresponding to the photon’s energy. Usually we can assume that the system was in the beginning in its lowest energy state called ground state, thus the frequencies at which absorption occures correspond to the energy levels of the system. Knowing the energy levels, conclusions can be drawn about the interactions between the components of the system.

The energy levels correspond to excitations of the system, for example coordinated vibrations of the crystal lattice (vibration of the atoms with an electric charge) or of the magnetic moments of the atoms. The former can be excited by the electric component and the second one by the magnetic component of the light with adequate polarization. For example a vibration of electric charged ions along the x axis can be excited by an oscillating electric field along the x axis.

In most materials these electric and magnetic excitations are independent of each other, each energy level can be characterized either as electric or magnetic vibration. In contrast, in multiferroics the coupling of electric and magnetic properties manifests itself also in the excitations of the system; the same levels can be reached both by an electric and magnetic transition. These two processes can either enhance or weaken the effect of each other, which depends on the direction of light propagation. This means, that the absorbtion of light can be different for light beams travelling from left to right and beams travelling to the opposite direction. This effect is termed as directional dichroism.

This research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 ‘National Excellence Program’.

In some materials the electric charges show a spontaneous ordering, giving rise to an electric polarization. This polarization can be reversed by an external electric field, and after the electric field is removed the material preserves its polarization state. This effect can be used to store information (Fe-RAM) with lower power consumption and faster writing/reading cycles than the commonly used flash memories. These materials are termed as ferroelectrics.

Other materials show a spontaneous ordering of atomic magnetic moments, which can be visualized as little arrows. If these moments point all in the same direction, they give rise to a net magnetization. This magnetization can be reversed by a sufficiently large external magnetic field. The magnetic state of the material can also be used to store information, as it is done in the case of hard drives. The materials showing magnetic ordering are termed as ferro- or antiferromagnets, depending on the parallel- or antiparallel ordering of the neighbouring moments.

If the two previous effects are simultaneously present, the material is called multiferroic. In this case the electric and magnetic properties are coupled: magnetic state can be modified by an external electric field and electric state can be influenced by an external magnetic field. This coupling can be either an inherent property of the material due to the so called spin-orbit coupling or can come from a mechanical gluing between a ferroelectric and ferromagnetic layer of two different materials. The first case is extremely interesting if we want to understand the microscpic mechanisms governing the electromagnetic properties of the material, and the second one can be promising in the point of view of future information technology applications. In my work I study multiferroic crystals with inherent magneto-electric coupling.

This research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 ‘National Excellence Program’.

About the blogger: I’m David Szaller, a PhD student working in the Magneto-Optical Spectroscopy Group of the Budapest University of Technology.

This research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 ‘National Excellence Program’.

19.04.2013.

Seminar: D. Szaller – “Reciprocity violation in multiferroics”

at Budapest University of Technology and Economics, Department of Theoretical Physics

Seminar: I. Kézsmárki – “Optical magnetoelectric effect in multiferroics”
Eötvös Loránd University, Nanophysics Group

Seminar (22.03.2013.): Prof. T. Hanscheid (Instituto de Medicina Molecular) – “Haemozoin: from melatonin pigment in a mad woman to drug target, immune-modulator and diagnostic tool”

22.02.2013.

Seminar: Á. Butykai – “Magneto-optical diagnosis of malaria”

Budapest University of Technology and Economics, Department of Theoretical Physics

07.02.2013.

V. Kocsis is back after 4-months-long crystal growing (~4×30×24 hours work ) at RIKEN