Group of Surface Magnetism / Ferromagnetic Resonance Laboratory

D e p a r t m e n t o f M a g n e t i s m a n d L o w T e m p e r a t u r e s
S i t e S l o v a n k a

Group of Surface Magnetism /
Ferromagnetic Resonance Laboratory
Zdenek Frait

Our lab is engaged in magnetic spectroscopy of low-energy magnons in microwave region. This methods has a couple of pros in comparison to others methods of characterization of magnetic materials:

FMR does not disturb energetical state of sample, because energy of microwave photon is approx. 0.6 K
FMR measures effective volume magnetization directly, not the magnetic moment of the sample.
FMR can determine lot of interesting physical properties, e.g. g-factor (ratio of the spin and orbital magnetism), damping constant (excited states lifetime), exchange interaction and anisotropies of different origin, interlayer exchange energy in superstructures.
FMR is very sensitive. Its use is highly convenient for nowadays popular low-dimension magnetism study (thin films, multilayers, wires, nanostructures).

Facility

classical electromagnet Varian 3800 (field -1 to 31 kG)
unique FMR spectrometer with very broad frequency range 8-104 GHz with lot of options:
- options for anisotropy measurement (in-plane, out-of-plane)
- options for magnetoelastic study (stressing of the sample)
- cryostat for low-temperature measurement (down to 4 K)
- furnace for high-temperature measurement (up to 700 K)
high-precision system for frequency measurement (up to 100 GHz with 8 digit precision)

Photo by Petr Sturc

Research

Thin films, multilayers, nanostructures, patterned structures

These topics are our main field of interest. We study both theoretically and practically extensive range of thin films structures. Mainly we are interested in Fe/Au, Co/Au, Co/Pt, Fe/Cr, Fe/Si, FeSi/Si and some Fe/RE systems. Experimentally we investigate excitation and propagation of magnons in these metallic ferromagnets and influence of exchange stiffness, anisotropy, interlayer exchange, damping, g-factor etc. Some of these results are evaluated using our own original theories of excitation of magnons.

Amorphous and nanocrystalline materials

In cooperations mainly with other laboratories we study broad set of nanocrystallic materials mainly FeNi, FeCo and CuCo alloys. We are interested in its magnetoelastic properties, origin of surface anisotropy and surface spin-wave modes generation.

Applications-GMR, sensors

In our lab are intensively studied materials for potential application as GMR magnetic sensors. GMR effect in Fe/Si, FeSi/Si and FeCr bilayers and multilayers and wedges is investigated. As a by-product we have develop an original method for contactless differential measurement of GMR effect at microwave frequencies.

Cooperations

Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava, Slovakia
AG Festkörperspektroskopie, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum, Germany
Institut für Halbleitertechnik, Technische Universität Carolo-Wilhelmina, Braunschweig, Germany
Department of Physics, Colorado State University, Fort Collins, USA
Department of Physics, Simon Fraser University, Burnaby, Canada

Grants

2000-2004: Correlation of structure and magnetism in novel nanoscale magnetic particles
Human Potential-Research and Training Network, European Community
1998-2000: Composite nanogranular magnetic materials
Grant Agency of Czech Republic 202/98/1292
2000-2003: Garnet thin films with minimum losses
National Science Foundation (US)

Recent publications

J.F. Cochran, A. Kurn and Z. Frait:
A comparative study of FMR and Brillouin light scattering on amorphous Fe₄₀Ni₄₀B₂₀
J. Magnetism and Magnetic Materials, Volume 210, Issue 1-3, February 2000
Z. Frait, P.Sturc, K. Temst , Y. Bruynseraede, I.Vavra:
Microwave and d.c. differential giant magnetoresistance study of iron/chromium superlattices
Solid State Communications 112 (1999) 569-573