Microscopic Techniques for Characterization of Magnetic Layers
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N. MEYENDORF*, I. ALTPETER*~, U. NEZLMANN*, J. HOFFMANN**", W. NICHTLPECHER***, H. GRIMM**** *Fraunhofer Institute Nondestructive Testing, University 37, 66123 Saarbruecken, Germany **Center for Materials Diagnostics, University of Dayton, Dayton OH 45469-0121 ***Exabyte Magnetics, Nuernberg, Germany; ****IBM, Mainz, Germany
ABSTRACT In recent years increasing interest in magnetic materials especially amorphous and nano crystalline layers has arised. Due to the magnetostrictive and magnetoresistive properties magnetic materials obtained high importance in sensor, actuator and memory applications. Therefore new methods to characterize magnetic and mechanical properties of magnetic materials are required. Two new microscopic techniques will be presented in this paper. INTRODUCTION Magnetic techniques are well established for the characterization of ferromagnetic materials, especially steels. However, in recent years the focus of interest turned to applications of nano-structured ferromagnetic materials in microsystem technology. These applications include magnetic storage techniques, the development of magnetic RAMs, the application of magnetoresistive sensors based either on the AMR- ore the GMR- effect or on magnetostrictive principles. Magnetic nano-structures or magnetic material components, such as magnetic particles can also be used for internal sensor applications in adaptive structures. technique
lateald resolution
measured quantities
remark
Lorentz microscopy
< 10nm
oonmponent of magnetisation, magnetic structure
vey high preparctions qudity requirements
Spin-Polaized Electron Microscopy20n
2nm
component of magnetisatlon, magnetic structure
very high prepaations quadity requirements
Magneto-Optiaal Methods
200 nm
component of magnetisation,
reflecting surface
_____________________
Magnfic Mcic
ower30 m
mc~netic structure sctterfiel f
PoWsoonmpylt
Soaning McningoHscPobe yxt
350nrn OI robe
qucilty requirements
oatef feldvery
30n
necessary
vey high preparations
ii
high preparations quality requirements
Table 1: Established magnetic microscopy techniques [1] Therefore, the characterization of magnetic properties and micromagnetic structures for nano-magnetic materials is very important. In particular, there is a need for techniques that allow nondestructive characterization of structures with high local resolution, to image magnetic
structures and especially to learn something about the remagnetisation processes. Well established microscopic techniques based on the KERR-effect, on electron microscopy or on the scanning of probes across the test surface, e.g. magnetic atomic force microscopy (MAFM) and HALL-probe microscopy (table 1) [1]. This paper describes the application of two new microscopic techniques, developed at the Fraunhofer Institute for Nondestructive Testing in Saarbruecken for the characterization of magnetic layers and magnetic layer systems. EXPERIMENTS 1. Photothermally modulated stray field (PMS) technique An intensity modulated laser beam is used to heat the f
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