Spin canting

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]. 

Spin-canting is conveniently studied by Mossbauer spectroscopy with large magnetic fields applied parallel to the y-ray direction. The relative areas of the six lines are given by 3 p l l p 3, where... 

Analysis of dc zero-field cooled (ZFC) versus field cooled (FC) X versus T or XT versus T data can be quite valuable in some circumstances. For organic systems, it allows confirmation of spin-canted ordering in a sample, where spin alignment in a domain is incomplete. ZFS and FC plots will diverge at the... 

Fig. 18. The magnetic ordering of Mn(III)-ion spins in RM11O3, R = La, Pr, Nd, Tb, Ho (and Y), in two adjacent (001) planes. Not shown is the spin canting to give a small ferromagnetic component along the c-axis for R = La, Pr, Nd. The numerical values refer to the spin periodicity just below 7n, after Brinks et al. (2001).

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. 

Figure 6 Spin canting in (a) a linear ferromagnet and (b) in a linear antiferromagnet...

The exchange strength is 2//A = —16.5 K for the chloride. While there is no overt canting observed in the data, the presence of the spin-canting terms in the Hamiltonian creates different temperature dependences for each of the three principle snsceptibUities. ... 

Fdd2 fi form (Banister et al. 1996). The result is that in the a structure neighbouring chains are antiparallel, while in they are all parallel. Due to these symmetry considerations the a modification cannot exhibit a so-called spin-canting mechanism (Carlin 1989) which can account for the transition from a low-dimensional antifer-romagnet to a weakly ferromagnetic state. However, these restrictions are absent in the P modification, and this mechanism, based to a large extent on the structural distinction between the two polymorphs, has been used to account for the fact that this p form is the first example of an open-shell molecule to exhibit spontaneous magnetization above liquid helium temperature (36 K). 

The orthoferrites, RFeOa, where R is yttrium or a rare-earth element have a structure based on a distorted perovskite lattice with only one iron environment. Most of them possess weak ferrimagnetic character as a result of spin canting from the ideal two-sublattice antiferromagnetic ordering. 

The iron borate FeaBOg is a weak ferroniagnet with a Curie temperature of 508 K [177]. The Mossbauer spectra show that below 415 K the spins of both types of iron site are perpendicular to the [100] axis, but above 415 K they are parallel to this axis. The ordering is basically antiferromagnetic but with spin canting. 

More detailed study of the magnetic moments and internal magnetic fields of the two iron sites in FeaP suggests that it is ferromagnetically ordered, rather than ferrimagnetically with spin canting [108]. 

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