ANISOTROPY OF COBALT-ADSORBED γFe₂O₃ PARTICLES

Abstract

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Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

“…When starting form a soft core (i.e., inverse structures) the opposite effects are found. Namely, M S decreases and H C rises as the amount of hard phase is increased [106,107,249,260,293]. However, in certain cases, if the difference in M S between the counterparts is small (e.g., hard Co-ferrite and soft Mnferrite both with M S ~ 80 Am 2 /kg (80 emu/g) at room temperature), although M S remains rather constant with the relative amount of hard and soft phase, H C does evolve according to the hard/soft volume ratio [101,102,143,[251][252][253]262,292].…”

“…However, in certain cases, if the difference in M S between the counterparts is small (e.g., hard Co-ferrite and soft Mnferrite both with M S ~ 80 Am 2 /kg (80 emu/g) at room temperature), although M S remains rather constant with the relative amount of hard and soft phase, H C does evolve according to the hard/soft volume ratio [101,102,143,[251][252][253]262,292]. There exist some systematic studies fixing the core size and methodically increasing the shell size both for conventional hard/soft and inverse soft/hard systems [93,99,101,102,114,125,[127][128][129]132,190,243,248,249,253,263]. The evolution of H C , decreasing roughly linearly as the volume fraction of soft counterpart is increased (see Fig.…”

Acicular gamma -Fe/sub 2/O/sub 3/ particles surface-coated with barium ferrite

“…fiowever, this is not true since: (1)no particles other than acicular ones can be visible in TEM, except those over-calcined, ( 2 ) the a -Fe203 without Ba++-treating tends to be easily sintered at temperatures above 75OoC while the treated ones remain un-sintered at temperature as high as 89OoC for 12 hours. Dark field micrographs of an S3JR2 sample, as -------…”

“…(1) mixing a 0.5 M FeC12 a solution and a 2.5 M NaOH solution ra$i81yl maintaining a pH of 13, && oxiding by pumping air into the solution for 200 min to precipitate acicular a-FeOOH particles, ( 2 ) washing and filtering with deionized water and drying,…”

Technical trends in recording tape fine particles. A short review

“…Among them the abrupt drop in coercivity and remanence for Cr02 at high temperature is due to its relatively low Curie point of 119.8 °C. The state of cobalt adsorption and anisotropy were discussed elsewhere (Tokuoka et al, 1977;Tokuoka et al, 1980).…”