double exchange theory

Double exchange theory explains how certain magnetic materials conduct electricity and become magnetic. It involves ions of manganese with different charges (Mn³⁺ and Mn⁴⁺) and their electrons. Electrons hop between these ions, and their ability to move freely depends on the alignment of the ions' magnetic moments (spins). When spins are aligned, electrons can hop easily, making the material both conductive and magnetically ordered. This interaction couples electrical conductivity with magnetism, explaining behaviors in materials like manganites. Essentially, the theory links electron movement to magnetic order, revealing how electron spin alignment influences both conductivity and magnetic properties.