Magnetic phases in iron-doped NiCl<sub>2</sub>
R J Pollard; C Bauer; V H McCann; R J Pollard; Dept. of Phys., Monash Univ., Clayton, Vic., Australia; C Bauer; Dept. of Phys., Monash Univ., Clayton, Vic., Australia; V H McCann; Dept. of Phys., Monash Univ., Clayton, Vic., Australia
Журнал:
Journal of Physics: Condensed Matter
Дата:
1991-07-29
Аннотация:
The magnetic phases of two concentrations of iron in Fe<sub>x</sub>Ni<sub>1-x</sub>Cl<sub>2</sub> (x=0.06 and 0.10) are reported from <sup>57</sup>Fe Mossbauer spectroscopy. Published data were used for x=0.06, and new data are presented for x=0.10. Substituting x=0.10 causes the ferrous moments to align along the crystallographic c-axis, whereas in pure NiCl<sub>2</sub> the moments are perpendicular to the c-axis. For x=0.06 parallel and perpendicular phases coexist, with the proportion of parallel moments decreasing smoothly from 74% at 4.2 K to zero at the Neel temperature (T<sub>N</sub>). The introduction of iron reduces T<sub>N</sub> from 52 K (x=0) to 46 K (x=0.10). A crystal field model was used to interpret temperature variations of the hyperfine parameters. The effective magnetic exchange constant for parallel moments is twice as large as that for perpendicular moments. In addition the Fermi contact constant B<sub>c</sub> is -50 T for parallel moments, compared with 40 T for perpendicular moments. A 6 T magnetic field applied along the c-axis for x=0.10 at 5 K induces a canting of the moments from the principal electric field gradient axis by 20-35 degrees , and it is inferred that under these conditions the system is in a spin-flopped state in which the ferrous ions experience nearly identical environments.
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