Intergranular Exchange Coupling in FePt:X:FePt ( ${\rm X}={\rm B}$ , C, ${\rm SiO}_{\rm x}$ ,

In this study we quantitatively determined the exchange coupling across B, C, SiO_x, Cr and TaO_x segregants by measuring the exchange coupling between two FePt layers separated by segregant layers of varying thickness. Our study indicates that the segregant that provides the best exchange break is TaO_x; whereas, C is the worst and SiO_x, Cr and B are in between. Our data indicates that a segregant intergranular region thicker than 0.8 nm should decouple FePt grains if B, TaO_x, SiO_x, or Cr are used, but with C, a thickness greater than 1 nm is required.