Magnetic properties of Ho₂Fe_17−xMn_x– influence of Mn substitution

Abstract

The structural and magnetic properties of Ho 2 Fe 17−x Mn x (x=0-5) have been investigated by x-ray diffraction, Mössbauer spectroscopy and DC magnetization measurements (0-5 T) over the temperature range 4.5-350 K. Similar to other ferrimagnetic R 2 Fe 17-x Mn x systems, the unit cell volume generally increases with Mn content other than for low Mn values where a slight maximum is detected around x ∼ 0.5. The nature of the magnetic phase transitions around T C is shown by Arrot plot analysis to be second order for all samples. The Curie temperature remains essentially unchanged for Mn contents up to x=1.0 (T C =336 K for x=0.0, T C =338 K for x=1.0) before decreasing steadily with further increase in Mn content (T C =209 K for x=5). The 57 Fe hyperfine interaction parameters have been determined from variable temperature Mössbauer spectra.

Magnetovolume effect in Ho2Fe17-xMnx compounds

“…2) lead to a magnetic transition temperature that agrees well with our magnetic data. 8 Figure 3 shows the temperature dependence of the volume expansion DV/V for the Ho 2 Fe 17-x Mn x compounds of T C values close to room temperature (the lattice parameters were derived from the ramp data using the Le Bail approach; detailed refinements will be presented elsewhere 12 ). Figure 3 reveals that the DV/V values for all samples tend toward linear behavior at high temperatures above T C , whereas pronounced Invartype behavior is observed below T C .…”

“…Details of the sample preparation methods and experimental procedures are presented elsewhere. 8 Neutron powder diffraction experiments (k ¼ 2.4191 Å ) have been carried out from 10 to 450 K using the high intensity powder diffractometer Wombat, OPAL, Australia. 9 Two series of variable temperature neutron diffraction measurements were undertaken on each sample after first cooling to base temperature T ¼ 10 K. The samples were initially investigated using a ramp sequence with a step of 1 K and counting time of 1 min at each temperature; this enabled the overall trends of the peak intensities and magnetic transitions to be delineated.…”

Critical behaviour of Ho 2 Fe 17 − x Mn x —magnetisation and Mössbauer spectroscopy

“…The Ho 2 Fe 17-x Mn x compounds (x = 0, 0.5, 1, 2) were prepared by standard argon arc-melting (see [5][6][7] for details). The magnetic measurements were carried out in magnetic fields up to 6 T over the temperature range 5-350 K using a Physical Property Measurement System [6,7]. 57 Fe Mössbauer spectra were obtained using a standard constant-acceleration spectrometer and a 57 CoRh source and the spectrometer calibrated at room temperature with an α-iron foil.…”

“…As below, we have carried out a detailed analysis of the magnetisation data around T C to investigate further the nature of magnetic phase transition in these compounds. The magnetisation data have been presented elsewhere [6,7] with the analytical approach following that described in the critical magnetic study of TbNi 2 Mn [9].…”

“…Recently we reported [6,7] that the substitution of Mn for Fe in Ho 2 Fe 17-x Mn x compounds leads to a minimum of M s at 10 K and a maximum of T C in the composition dependence of M s (at T=10 K) and T C as well as the presence of strong magnetovolume effects below T C . In order to better understand the nature of the magnetic phase transition around T C in these systems, we have carried out a detailed investigation of the critical behaviour by DC magnetization measurements and Mössbauer spectroscopy with the main findings reported here.…”