Figure 1.

Equilibrium deflection 〈ψ〉 of an elastically coupled permanent magnet as a function of the orientation θ₀ of the external field with respect to the rest orientation of the magnet ψ = 0, for various values of mH and K. Ratio mH/K increases from (a) to (e). Solid line, 〈ψ〉, thermal equilibrium value of deflection (equation (C 2)); grey area, angular scatter ±Δψ about 〈ψ〉 (equation (C 4)); blue dashed line, mechanical equilibrium value of deflection ψ; red dotted line, approximate mechanical equilibrium deflection according to equation (3.4a) in (a,b) and equation (3.4b) in (c). Note the strong increase in angular scatter on going towards the antiparallel field orientation (θ₀ = 180°) once mH/K ∼1, in (d) and particularly in (e). (f) Zoom-in on the unstable region in (e). (a) mH = 25kT, K = 300kT; (b) mH = 50kT, K = 300kT; (c) mH = 25kT, K = 50kT; (d) mH = 25kT, K = 25kT; (e) mH = 25kT, K = 15kT.