$L1_{0}$ FePt/Fe Exchange Coupled Composite Structure on MgO Substrates

Abstract

A core-shell type exchange-coupled composite (ECC) structure is developed with an L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> phase FePt core and an Fe shell. Coercivity decreases from 30.6 kOe for the FePt granular film with a very thin thickness of 3.2 nm, to 7.85 kOe for the FePt/Fe core-shell type granular film with a 3-nm-thick Fe. The energy barriers of the FePt/Fe films are measured by using Sharrock equation. A modified formula of gain factor considering the effect of films' thickness is proposed. Core-shell type FePt/Fe ECC granular film has a large advantage over a conventional granular film for media application.