Evaluation of blocking temperature and its distribution for L10-type FePt granular films

The blocking temperature (T (B)) and blocking temperature distribution (Delta T (B)) of magnetic grains were evaluated for L1(0)-type FePt granular films with various grain boundary materials (GBMs). T (B) and Delta T (B) were measured from remanent magnetization. The relationship between the degree of order and Curie temperature (T (C)) for the L1(0)-type FePt phase was separately evaluated using alloy films. According to actual measurements, the obtained mean T (B), mean T (B)/T (C) and Delta T (B) for granular films were 620 K, 0.83 K, and 200 K, respectively, for SnO GBM film and 450 K, 0.61 K, and 260 K, respectively, for TiO2 GBM film. Based on these values, mean T (B), mean T (B)/T (C), and Delta T (B) were calculated assuming that tau = 2 x 10(-7) s, which is the relaxation time, corresponds to the HAMR writing time. These were 737 K, 0.98 K, and 24 K, respectively, for SnO GBM film and 685 K, 0.93 K, and 72 K, respectively, for TiO2 GBM film. These results for granular films can be useful for designing a hard disk drive with HAMR.

Automated summary

This study evaluated the blocking temperature (T (B)) and blocking temperature distribution (Delta T (B)) of magnetic grains in L1(0)-type FePt granular films with different grain boundary materials (GBMs). T (B) and Delta T (B) were measured from remanent magnetization. The relationship between the degree of order and Curie temperature (T (C)) for the L1(0)-type FePt phase was separately evaluated using alloy films. The obtained mean T (B), mean T (B)/T (C), and Delta T (B) for granular films with SnO GBM were 620 K, 0.83 K, and 200 K, respectively, while for granular films with TiO2 GBM, they were 450 K, 0.61 K, and 260 K, respectively. Based on these values, mean T (B), mean T (B)/T (C), and Delta T (B) were calculated assuming a relaxation time of 2 x 10(-7) s, which corresponds to HAMR writing time. For SnO GBM film, these values were 737 K, 0.98 K, and 24 K, respectively, and for TiO2 GBM film, they were 685 K, 0.93 K, and 72 K, respectively. These results for granular films can be useful for designing a hard disk drive with HAMR.