Solution

ID: past-exam-of-the-chemistry-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-2/section-b/21/f/solution

For Co, the full field-polarized ionic value is
This is distinct from the much smaller weak-ferromagnetic domain moment, approximately 450 G cm mol at low field. A low-temperature isothermal loop should have a small hysteretic central component superposed on the antiferromagnetic field response. Reversal changes the selected weak-ferromagnetic domain and produces remanence and coercivity. At larger fields the magnetization continues to increase as the opposed sublattice moments rotate; a spin-flop or spin-reorientation feature may occur depending on field direction and anisotropy. Only sufficiently strong fields approach the full ionic saturation value, so the small low-field loop must not be labelled as saturation at 4.25 .

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