Morphology and domain pattern of L1 ordered FePt films

Abstract

Magnetic force microscope (MFM) was used to characterize the L10 ordered FePt(001) films sputter deposited directly on MgO(001) substrates at an elevated temperature. With the change of nominal thickness (tN), the morphology varied from isolated particles to continuous films. The coercivity showed a marked change at the percolation boundary of tN≅45 nm, where the film morphology changed from a discontinuous to a continuous state. Below tN=45 nm, the coercivity did not change apparently, though the number of single-domain particles increased gradually with decreasing tN. At tN=20 nm, a critical (maximum) size of single domain particles, d=180 nm, was obtained from a size distribution, which was taken from the atomic force microscope/MFM measurement. The value calculated for this critical size was found to be d=155 nm in the assumption that the particles had ellipsoidal shape. The slight difference between experimental and theoretical values is likely to be attributed to an axis ratio (c/a) distribution of particles.

Domain size correlated magnetic properties and electrical impedance of size dependent nickel ferrite nanoparticles

“…This is in good agreement with the reported results for the particles to be in a single domain state. 25,[27][28][29][30][31] This is also in good agreement with the theory of demagnetizing field for smaller particles. The charges developed on the surface will act as a source of demagnetizing field.…”

“…et al reported 380 nm for spherical particles. 24,25 Xavier et al have reported that the critical size equals to 35-40 nm for spherical particles. 26 Recently, Mahmoud et al reported that the critical size for a single domain particle is 16 nm with M s = 30 emu/gm at H c =280 Oe, and also he reported the maximum M s of 41.82 emu/g for the crystallite size of 30 nm annealed at 1000 o C. 27 Jing et al presented that the particle of size 41.6 nm, gives M s of 45 emu/g at H c =86.3 Oe and reported as a single domain particles.…”

Nanostructured MnGa films on Si/SiO2 with 20.5 kOe room temperature coercivity

“…In the low-rate sample, each island is magnetically isolated from all other islands, and the global magnetic properties of the film correspond to the sum of all individual islands. We can estimate the critical size, d C , for single domain behavior using 24 where K u , A, and N are the uniaxial anisotropy, the exchange stiffness constant, and the demagnetization factor, respectively. Using (Fig.…”

High resolution magnetic force microscopy of patterned L10-FePt dot arrays by nanosphere lithography

“…The transition from a double domain to a single domain state is not expected to be clear cut, given the fluctuation of the shape and size of the dots. It is interesting to note that the critical single domain size of our in-plane magnetized L1 0 -FePt dots is about half the previously reported values (about 180-340 nm) [24,25] for out-of-plane magnetized dots. The difference is worthy of further investigation.…”