  The spin Hall magnetoresistance (SMR) phenomenon includes the fundamental
physics of spin current, and originates from spin accumulation at an interface
owing to the spin Hall effect. Although bilayers are the simplest structure
exhibiting SMR, these exploit spin accumulation at only one side of a layer.
Herein, trilayers of CoFe2O4/Pt/CoFe2O4 were fabricated and their spin Hall
magnetoresistance was investigated. The trilayer structure featuring a thin Pt
layer exhibited an SMR ratio four times that of a CoFe2O4/Pt bilayer. Further,
the SMR ratio exhibited a dependence on Pt layer thickness that can be
attributed to interference of the spin accumulations at both sides. Herein,
several parameters such as spin diffusion length and mixing conductance were
derived using the theory of Chen et al.
