H+2 ion-implantation effect in vacuum-evaporated permalloy films

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Abstract
This letter reports that the magnetoresistance ratio Δ ρ/ρ increases and the coercive force Hc reduces in vacuum‐evaporated permalloy films by implanting H+2 ions. The increase in Δ ρ/ρ is due to a decrease in the resistivity ρ, and the magnetoresistance coefficient Δ ρ remains almost unchanged. By implanting H+2 ions ρ becomes nearly equal to that of the permalloy bulk in the film thickness range of more than 3000 Å. The coercive force Hc remarkably decreases to the small value in the thinner films range. The grain size of ion‐implanted films is about the same as that of non‐ion‐implanted films. This shows that the decrease in ρ is not due to the grain growth mechanism as in annealed films but may be due to some mechanism of the grain boundary change caused by implanted ions. The mechanism of decrease in ρ and Hc remains to be clarified.