Recently, the world's first rotatable magnetic force microscope (MFM) in a superconducting magnet is invented in the lab of Professor LU Qingyou Hefei Institutes of Physical Science, Chinese Academy of Sciences.
The direction of magnetic field is changed from parallel to vertical to sample surface continuously while the magnetic probe and sample are rotated together, which realizes measurement of magnetic domain on anisotropic materials under different magnetic field direction with the help of non-vector superconducting magnet.
It’s discovered that the direction of magnetic moment is changed as direction of magnetic field changing, but magnetic moments are always constrained by domain walls during domain characterization of La2/3Ca1/3MnO3 (40 nm) on NdGaO3 substrate.
This invention and discovery entitled “A mechanical rotatable magnetic force microscope operated in a 7 T superconducting magnet” was published on famous microscopy journal Ultramicroscopy.
Magnetic field has to be vertical to sample surface during characterization process by MFM because of restriction of bore size of traditional magnet. So, the relations between direction of magnetic field and magnetism of anisotropic materials are usually omitted due to this reason, which is the common defect for MFM to characterize anisotropic magnetic materials. Vector magnet can avoid this problem and generate a low magnetic field but cost too much. These two problems are solved decently by rotatable MFM.
A compact MFM is invented by transforming “SpiderDrive” to get rid of restriction of bore size of 7T superconducting magnet. This MFM and sample can be rotated continuously in 7T superconducting magnet so that 7T magnetic field can be implemented on sample from any direction between 0 to 90 . Meanwhile, measurement temperature ranges from liquid helium temperature to room temperature.
Researchers use anisotropic material La2/3Ca1/3MnO3 (40 nm) on NdGaO3 substrate to test this device. It’s found that direction of magnetic moment is changed and N-S structure is formed within sample surface while the angle between magnetic field direction and normal of sample surface changes from 0 to 90 .
However, magnetic moments are always constrained by domain wall. The invention of this device provides a platform to characterize anisotropic magnetic materials under different directions of high magnetic field.
