Reentrant ferromagnetic ordering of the random-field Heisenberg model in <i>d &gt; 2</i> dimensions: Fourier-Legendre renormalization-group theory

The random-magnetic-field classical Heisenberg model is solved in spatial dimensions d >= 2 using the recently developed Fourier-Legendre renormalization-group theory for 47r steradians continuously orientable spins, with renormalization-group flows of 12 500 variables. The random-magnetic-field Heisenberg model is exactly solved in 10 hierarchical models, for d = 2, 2.26, 2.46, 2.58, 2.63, 2.77, 2.89, 3. For nonzero random fields, ferromagnetic order is seen ford > 2. This ordering, at d = 2.46, 2.58, 2.63, 2.77, 2.89, 3, shows reentrance as a function of temperature.