Spiral antiferromagnet

The Yoimg s modulus anomaly arising at the transition from the paramagnetic to the hehcal phase in a single-domain spiral antiferromagnet, which belongs to the 6 mm (D i,) Laue class, was considered by Spichkin and Tishin (1997). 

Fig. 39. The different magnetic structures of HoNi2 B2C as determined by neutron scattering, (a) Commensurate antiferromagnetic, (b) incommensurate restructure (spiral) with the modulation vector T2 = (0.0,0.916) and (c) proposal how the incommensurate a -structure looks like (Loewenhaupt et al. 1997). Its modulation vector is...

Amici and Thalmeier (1998) used the quasi one-dimensional model mentioned in Section 4.9.1. In their approach the presence of ferromagnetically ordered Flo layers with the magnetic moments oriented perpendicular to the tetragonal c-axis is adopted and the competition of the RKKY interaction along the c-axis with the crystalline electric field is analyzed in order to determine the transition between the commensurate antiferromagnetic structure and the incommensurate c spiral shown in Figure 39. 

The parameters rp and 7J2 are linear combinations of the magnetic modes converted on the representation T5. The fact that below TN the magnetic subsystem of copper metaborate forms an easy-plane weak ferromagnet, twisted below 7] in a spiral, permits to compose rp as a combination of the ferromagnetic modes (1) and (3), and tj2 as a combination of the antiferromagnetic modes (2) and (4). Accordingly II = (Hn, Hn) = (Hx, -Hy). It is necessary to note that in the thermodynamic potential given by Eq. (5) the order parameter responsible for the transition at 7] is not chosen in an explicit form as it was done in our previous paper [8],... 

One of these models is the spin- ladder with competing interactions of the ferro- and antiferromagnetic types at the F-AF transition line. The exact singlet ground-state wave function on this line is found in the special form expressed in terms of auxiliary Bose-operators. The spin correlators in the singlet state show double-spiral ordering with the period of spirals equal to the system size. 

A spiral configuration with [230] screw axis, 4> — 2w/15, spins within (140), and antiferromagnetism along c axis is reported. 

Fig. 38. Antiferromagnetic-spiral configuration with k [001]. (After Kaplan, Dwight, Lyons, and Menyuk (331).)...

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