Magnetic field analysis
Iatia's QPI is capable of producing magnetic field maps of samples.
Magnetic fields effect the phase of electrons in transmission electron microscopy. QPI calculates the phase distribution and is able to render that information as a magnetic field map showing strength and direction of the magnetic field.
Case study - manganese trioxide
The following study was conducted by HREM Research, Inc (Japan) on a Perovskite-type manganese trioxide (Pr1-x(Ca1-y,Sry)xMnO3 (x=0.45, y=0.4))1.
A through focus series of 3 images at 2mm steps was taken using a Hitachi HF-3000L Lorenz microscope at approximately 2,000x magnification. Phase distribution maps were generated with QPt for DigitalMicrograph™ incorporating QPI technology.
Brightfield
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QPI phase map
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Magnetic field map
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The above image shows the restored phase and a magnetization vector map obtained from the gradient of the phase distribution. The direction and amplitude of the magnetization are represented by changes in color and brightness, respectively. The green and violet stripe pairs in the image reflect the region with opposite magnetic orientation. Darker areas represent smaller amplitudes of the local magnetization.
It is clear, from the magnetic field map of this sample, that magnetization directions are parallel to the elongated domain directions. In addition, the wide (180o) domains and the narrow (stripe) domains magnetize perpendicular to each other.
References
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Phase Measurement in Electron Microscopy Using the Transport of Intensity Equation
Kazuo Ishizuka, and Brendan Allman, Microscopy Today, 13, 22-24 (2005). -
Real Space Observation of Helical Spin Order
M. Uchida, Y. Onose, Y. Matsui, and Y. Tokura, Science, 311 359-361 (2005). -
Determining the Magnetic Potential in Patterned Materials Using Energy-Dependent Lorentz Phase Microscopy
A. Kohn, A. K. Petford-Long, and T. C. Anthony, Phys. Rev. B., 72, 014444 , (2005).