Nd₂Fe₁₄B

Fig. 1 MOKE image of the fractal domain pattern of Nd₂Fe₁₄B taken in the group of our collaborator Prof. Ruslan Prozorov.

The rare-earth magnetic alloy Nd₂Fe₁₄B is one of the strongest known permanent magnets and is widely used in industrial and commercial applications. In the thermally demagnetized state, Nd₂Fe₁₄B magnets display a high degree of fine-scale (~25nm) magnetic texture [1-2] and branched fractal-like domains [3-4] along the c-axis, that make them of interest for magnetic microelectromechanical applications (`Mag-MEMS'). This material has been studied in the past using magnetic force microscopy (MFM) [1,2,4,5], scanning electron microscopy (SEM) [5], and magneto-optic Kerr effect (MOKE) microscopy [3,4,6]. Our magnetic force microscope has additional cababilities that enable us to study the magnetic domains at smaller length-scales and lower temepratures than previous studies. Furthermore, we employ harder magnetic tips which we hope to use for domain manipulation.

[1] M. Al-Khafaji et al. "The effect of tip type and scan height on magnetic domain images obtainsed by MFM." IEEE Trans. Magn. 32, 4138 (1996).
[2] M. Al-Khafaji et al. "The origin an interpretation of fine scale magnetic contrast in magnetic force microscopy: a study using single-crystal NdFeB and a range of magnetic force microscopy tips." J. Appl. Phys. 83, 6411 (1998).
[3] A. Kreyssig et al. "Probing Fractal Magnetic Domains on Multiple Length Scales in Nd₂Fe₁₄B." PRL 102, 047204 (2009).
[4] W. Rave et al. "Observations on high-anisotropy single crystals using a combined Kerr/magnetic force microscope." JMMM 177, 1474 (1998). [5] W. Szmaja. "Investigations of the domain structure of anisotropic sintered Nd-Fe-B-based permanent magnets." JMMM 301, 546 (2006).
[6] M. Al-Khafaji et al. "Magnetic force imaging of domain structures for a (Pr/Nd)FeB alloy." J. Appl. Phys. 83, 2715 (1998).