Determining the low-coercivity temperature coefficient in FePt (fct)/FePt (fcc) nanocomposite films

• Published in: Journal of physics. Conference series 2010-01, Vol.200 (7), p.072106
• Main Authors: Zhang, W Y, Shima, H, Takano, F, Akinaga, H, Nimori, S
• Format: Article
• Language: English
• Subjects: Coercivity; High temperature; Intermetallic compounds; Iron compounds; Magnetic films; Magnetic saturation; Multilayers; Nanocomposites; Physics; Platinum; Platinum compounds; Remanence; Silicon dioxide
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/200/7/072106

High-coercivity Fe100-xPtx (x 47.4–54.1) nanocomposite films were synthesized using post-annealing Si-SiO2/[Fe2.7Pt1.3(y)/Pt(z)]n multilayers. The soft magnetic face-centered cubic (fcc) phase was exchange-coupled with a hard magnetic face-centered tetragonal (fct) phase in all the films. As x was increased, the volume fraction of the fct phase in the film increased, while the saturation magnetization decreased. The coercivity and remanence ratio of the film increased linearly from 5.8 kOe and 0.67 at x 47.4 to 13.7 kOe and 0.74 at x 54.1, respectively; this increase can be attributed to the effect of Pt addition, which increases the content and the chemical ordering degree of the fct phase. Over the temperature range of 200–600K, the coercivity temperature coefficient (CTC) at x 48.3 was 0.15%/K—a value that is 4.1 times lower than the CTC of a previously reported Nd2Fe14B film (0.77%/K). Pt addition led to a significant decrease in CTC within 200–600 K down to 0.08%/K at x 54.1. The high coercivity, together with very low CTC, indicates that FePt(fct)/FePt(fcc) nanocomposite films are the excellent candidates for high-temperature applications of permanent magnetic film.