One-Dimensional Boson Fields in the Critical Range of EuS and EuO

Following the principles of renormalization group theory the typical experimental indications are discussed that in ordered magnets with a three-dimensional spin the dynamics of the spins is controlled by a boson guiding field instead by exchange interactions to the neighboring spins. The spins are, so to say, sensors to probe the dynamics of the relevant boson field. It is evident that these findings are not complementary but fundamentally different from atomistic concepts. The bosons are essentially magnetic dipole radiation emitted upon precession of the ordered moments. Within the individual domain the one-dimensional field has the character of a laser field. The field aligns all spins along its axis. In order that in cubic magnets three-dimensional dynamic symmetry can result a vector average over all one-dimensional boson fields of the individual domains is necessary. It is argued that this averaging process does not work in the critical temperature range of cubic EuS and EuO. As a result, the critical behavior of EuS and EuO is that of the one-dimensional boson field of the isolated domain and agrees with the critical behavior of the one-dimensional antiferromagnet MnF2. For the magnets with 1D boson field and half-integer spin it is found that the rational exponents β = 1/3, γ = 4/3 and ν = 2/3 give an excellent account of the mean exponent values over the most accurately known experimental data. These exponents obey the scaling relation 2β = 3ν − γ