Analytical Instruments
Analytical Instruments
HOLMARC MOKE LB215 is an easy to use magneto-optical Kerr effect (MOKE) laser based system which provides a convenient way to obtain the changes in magnetic moment at different fields and temperatures. 408nm, 532nm and 650nm Diode lasers are used for the measurements.
Lock-in amplifier technique is employed in this instrument and the modulation is performed with an optical modulator. Sample is mounted in the center of the magnet with its surface either parallel or perpendicular to the field. The supplied high field, variable gap, dipole electromagnet allows the user to apply large fields (approx. 20,000 Gauss at 10 mm pole gap) in a longitudinal or perpendicular geometry to study hard magnetic materials. HOLMARC MOKE LB215 is supplied with ORMS software. It can manage data collection and data manipulation fast and accurate.
The magneto-optical Kerr effect is a well established technique to study magnetization properties. The effect is based on the fact, that the plane of polarization of light is rotated when the light is reflected from a magnetic material. The physical origin of MOKE is the magnetic circular dichroism effect: exchange and spin-orbit coupling in a magnetic material lead to different absorption spectra for left- and right-circularly polarized light. Measuring the change of polarization of reflected beam (often referred to as Kerr angle θKerr) gives access to the magnetization state of the sample.
MOKE is particularly important in the study of ferromagnetic and ferrimagnetic films and materials. In this non-destructive surface sensitive technique, polarization-modulated laser light reflects from a magnetic surface in the presence of a sweeping magnetic field. Since light is an electromagnetic field, it's not surprising that the magnetic field of the sample interacts with the light to cause a very slight change in the light's polarization and ellipticity. We measure these changes in the light as an intensity change through nearly crossed polarizers, recording the intensity as a function of the applied magnetic field.
Using this instrument Polar, Longitudinal and Transverse Magneto-optic kerr effect can be studied. Longitudinal and polar configurations are used as routine tools for the magnetic characterizations of films. A dedicated room-temperature set-up provides for quick acquisition of in-plane hysteresis loops. These hysteresis loops provide information on the magnetic an isotropy presence in the film, and in the case of multi layers on the coupling between the layers. In the longitudinal Kerr effect, measurements yields qualitative information regarding alignment of magnetic moments in the surface plane of the sample. Measurement of the magnetization component perpendicular to the sample surface can also be studied using this setup.
Configurations for MOKE experiments
There are three configuration for MOKE experiments namely Polar, Longitudinal and Transverse configurations. These arise from the direction of the magnetic field with respect to the plane of incidence and the sample surface.
Polar MOKE
For polar MOKE, the magnetic vector is parallel to the plane of incidence and normal to the reflecting surface.
Longitudinal MOKE
For longitudinal MOKE, the magnetic field is parallel to both the plane of incidence and the sample surface.
Transverse MOKE
For the transverse MOKE geometry, the magnetic field is normal to the plane of incidence.
Established in 1993, Holmarc Opto-Mechatronics Ltd manufactures variety of scientific and engineering instruments for research, industry and education.
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