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Unidirectional coercivity enhancement in exchange-biased Co/CoO
T. Gredig, I. N. Krivorotov, P. Eames, and E. D. Dahlberg
A unidirectional coercivity enhancement, exhibiting the same behavior as a
positive exchange bias, has been discovered in a temperature range below
the blocking temperature in Co/CoO bilayers. Below this temperature range,
the usual shift of the center of the M–H loops to the negative or
antiparallel to the cooling field direction is found. This behavior is
observed in both magnetic hysteresis loops and transport properties. The
positive exchange bias can be explained by reversible changes in the
interfacial pinning by the antiferromagnet causing an asymmetric
magnetization reversal and a unidirectional coercivity enhancement along
the cooling field direction