Tunable negative and positive coercivity for SmCo∕(Co∕Gd) exchange springs investigated with SQUID magnetometry

S. Demirtas; M. R. Hossu; M. Arikan; A. R. Koymen; M. B. Salamon

doi:10.1103/PhysRevB.76.214430

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Tunable negative and positive coercivity for SmCo∕(Co∕Gd) exchange springs investigated with SQUID magnetometry

S. Demirtas, M. R. Hossu, M. Arikan, A. R. Koymen, M. B. Salamon

DOI 10.1103/PhysRevB.76.214430 · Physical Review B

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Abstract

Temperature dependent static magnetic properties of Co∕Gd multilayers, grown on SmCo, are experimentally investigated by means of SQUID magnetometry. The SmCo∕(Co∕Gd) system shows an exchange spring behavior above the compensation temperature (Tcomp) at which the magnetization of the antiferromagnetically coupled multilayer is zero. Below Tcomp, a tunable negative coercivity state (inverse hysteresis) appears, due to the coupling between the hard SmCo and soft Co∕Gd multilayers, irrespective of whether Co or Gd is proximate to the SmCo. However, for the strongly ferromagnetically coupled Co interface layer, negative coercivity persists over a larger temperature interval. The negative coercivity state vanishes if the coercivity of the SmCo layer is increased by controlling the Cu underlayer thickness.