Magnetic patterning of $Fe∕Cr∕Fe(001)$ trilayers by $Ga+$ ion irradiation

Magnetic patterning of antiferromagnetically coupled epitaxial $Fe(10nm)∕Cr(0.7nm)∕Fe(10nm)(001)$ trilayers by irradiation with $30keV$ $Ga+$ ions was studied by means of atomic force microscopy, magnetic force microscopy, and Kerr magnetometry. It was found that within a fluence range of $(1.25−5)×1016ions∕cm2$ a complete transition from antiferromagnetic to ferromagnetic coupling between the two Fe layers can be achieved. The magnetization reversal processes of the nonirradiated, antiferromagnetically coupled areas situated close to the irradiated areas were studied with lateral resolution. Evidence for a lateral coupling mechanism between the magnetic moments of the irradiated and nonirradiated areas was found. Special attention was paid to preserve the flatness of the irradiated samples. Depending on the fluence, topographic steps ranging from $+1.5to−2nm$ between the nonirradiated and irradiated areas were observed. At lower fluences the irradiation causes an increase of the surface height, while for higher fluences the height decreases. It was found that for the particular fluence of $2.7×1016ions∕cm2$ no height difference between the irradiated and nonirradiated areas occurs. The results suggest that the irradiation of $Fe∕Cr∕Fe$ trilayers with midenergy ions is an innovative method for magnetic patterning, preserving the initial smoothness of the sample.