Time- and space- resolved BLS setup


This measurement subsystem is designed for investigations of stationary and non-stationary spin-wave phenomena in transparent dielectric magnetic films. The propagation of spin waves can be followed at distances up to several tens of millimeters.

The simplified layout of the measurement setup is shown in the following figure.


  1. The sample - transparent magnetic film is mounted onto the holder, which allows positioning of the film in two dimensions (XY) with the accuracy of 1 micrometer. The full travel distance accounts 30 mm for each direction.
  2. The holder is placed into an electromagnet with the pole gap of 200 mm providing a uniform static magnetic field of up to 1 T.
  3. Excitation of waves of magnetization is realized by means of a microstrip antenna fed from the amplified microwave generator. Similar antenna is used to receive the waves after they propagated in the film for several millimeters.
  4. For space- and time-resolved detection of spin waves the probing laser light is focused onto the film by the objective L1. The objective L2 collects the light passing through the film and sends it to the interferometer for analysis.

Analyzing the intensity of light inelastically scattered by magnetic excitations in different spatial points of the magnetic film, two-dimensional maps showing the spatial distributions of dynamic magnetization in the sample are reconstructed. A typical map with dimensions of 1x1.5 mm2 is shown in the following figure.


 Using a pulsed excitation and a stroboscopic time-of-flight detection technique the setup allows the recording of the two-dimensional maps with temporal resolution better than 1 ns. An example illustrating propagation of a wide nonlinear spin-wave packet with duration of 50 ns recorded using this technique is presented in the next figure. The four panels show the two-dimensional maps of the dynamic magnetization recorded at propagation time as indicated.


The BLS setup is used for investigations of linear and nonlinear propagation of spin waves and spin-wave packets. Among the most significant observations made by means of this technique one can enumerate the discovery of nonlinear two-dimensional spin-wave bullets, the observation of spin-wave tunneling through a potential barrier, and the observation of formation of spin-wave nonlinear spatial patterns. Recently the technique was successfully applied for investigations of thermodynamics of magnon gas. These studies allowed us to discover Bose-Einstein condensation of magnons at room temperature.

Institut für Angewandte Physik
AG Demokritov/Nichtlineare Magnetische Dynamik

Corrensstraße 2
· 48149 Münster
Tel: 0251 - 83 3 35 51 · Fax: 0251 - 83 3 35 13