Model explaining magnetic phases and behavior in Ruthenium-based superconducting ferromagnets
A complete model has been developed to explain the sophisticated magnetic behavior in Ruthenium (Ru) based superconducting ferromagnets. In the complex system of Ru-materials, always consisting of at least two interacting magnetic species, multiple magnetic transitions have been observed. The superposition of corresponding ferromagnetic signals has been proposed to be responsible for producing features compatible with spin glasses, superparamagnetism, ferromagnetism, and antiferromagnetism. Slight differences in the temperature dependence of the Ru-species and the similarity in their magnetic behavior induce the rich phase diagram, which is enabled by the structural (hence, magnetic) inhomogenity and clustering. The combination of microstructural, magnetic and transport measurements along with careful analysis of the nonlinear ac susceptibility has allowed us to understand the spin ordering in these cluster systems, and establish the cohesive model working in the entire temperature and field ranges.