Canted-spin

Defects in ferrimagnetic structures often lead to noncollinear (canted) spin structures. For example, a diamagnetic substitution or a cation vacancy can result in magnetic frustration which leads to spin-canting such that a spin may form an angle 6c with the collinear spins in the sample [80, 81]. Similarly, the reduced number of neighbor ions at the surface can also lead to spin-canting [80-83]. 

CAH canted-spin antiferromagnetic insulator OO orbital-ordered... 

Fig. 28. Tentative phase diagram for LaMnC)3+5, 0 < <5 < 0.18. Data from Topfer and Goodenough (1997b). PI = paramagnetic insulator, CAFI = canted-spin antiferromagnetic (A-type) insulator, SGI = spin-glass insulator, FI = ferromagnetic insulator, MCS = metamagnetic canted-spin configuration.

Neutron-scattering experiments by Vasiliu-Doloc et al. (1998a) on an x = 0.15 sample showed the ferromagnetic order below 7c = 235 K developed a canted-spin structure below... 

Reference (261a) reports uniaxial ([100] of pseudocell) antiferromagnetisra 81.5°K < T < 88.3°K, parasitic ferromagnetism due to canted spins T < 81.5°K as a result of different single-ion anisotropies, thermal hysteresis in the canted-spin uniaxial-spin transition, and an He 9000 oe for field-induced spin canting in the intermediate temperature range. 

Antiferromagnetic sheets, but coupling between sheets gives noncollinear, canted spin structure. The two spin directions alternate in successive sheets along the c axis. Spin vectors lie in y-z plane at alternately clockwise and counterclockwise angles of 25 =fc 2° from the b axis. 

Spin-only moments would give /z = l/z5 and 0hb, respectively. Since the spins are in the (111) plane (303), a contribution to the ferrimagnetic moment should come from a canted-spin configuration. Orbital contributions to the g factor must also be playing a role, especially in the case of Co2+. It was pointed out in the discussion on rock salt structures that Co2+ in CoO carries an atomic moment of 3.7hb rather than the spin-only value of 3.0/z, and that this moment can be accounted for quantitatively if orbital considerations are included. 

Fig. 7.9. Schematic representation of the orientation of magnetic moments in ordered materials (a) ferromagnetics (b) antiferromagnetics (c) ferrimagnetics (d) canted spin materials.

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