Domain walls and macroscopic spin-flip-like metamagnetism inGdxCo1−x∕GdyCo1−yexchange-coupled double layers

Abstract

Amorphous ferrimagnetic ${\mathrm{Gd}}_{x}{\mathrm{Co}}_{1\ensuremath{-}x}∕{\mathrm{Gd}}_{y}{\mathrm{Co}}_{1\ensuremath{-}y}$ exchange coupled double layers (ECDL) have been prepared in order to investigate the magnetization reversal processes and the presence of stable magnetic configurations when the chemical compositions of both layers are very similar. The ECDL samples have been grown by co-sputtering from independent pure Co and Gd targets, being $100\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ the thickness of each layer. The measurements have been done by the magneto-optical Kerr effect at both sides of the ECDL in the temperature interval $200\phantom{\rule{0.3em}{0ex}}\mathrm{K}--450\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and the compositions of the two layers are $x=0.22$ and $y=0.24$. A rich variety of behaviors has been found, being the most relevant of those in the temperature range between the compensation temperatures $({T}_{\mathit{comp}})$ of both layers. Some of these observed behaviors include magnetization reversal by creation/annihilation of a Bloch wall across the ECDL thickness, and a macroscopic spin-flip-like metamagnetic state where the magnetic moments form a double antiferromagnetic state with the presence of an extended Neel wall when the magnetizations of both layers are similar. A temperature phase diagram for the transition fields between different magnetic states has also been deduced, being in very good agreement with the magnetic behavior observed in the whole temperature range.