We have studied the uniaxial magnetic anisotropy of Co/Pd superlattices grown under identical conditions by molecular-beam epitaxy along the three crystal axes: [001], [110], and [111]. Our measurements unambiguously demonstrate that the large systematic variations of the anisotropy energy with crystal orientation result solely from differences in the volume contribution to the anisotropy. We find the perpendicular interface anisotropy to be independent of the epitaxial orientation (0.63 ± 0.05 erg/cm 2 ), and hence to be an intrinsic property of the Co/Pd interface.

Real quantum heat engines lack the separation of time and length scales that is characteristic for classical engines. They must be understood as open quantum systems in non-equilibrium with timecontrolled coupling to thermal reservoirs as integral part. Here, we present a systematic approach to describe a broad class of engines and protocols beyond conventional weak coupling treatments starting from a microscopic modeling. For the four stroke Otto engine the full dynamical range down to low temperatures is explored and the crucial role of the work associated with the coupling/decoupling to/from reservoirs as an integral part in the energy balance is revealed. Quantum correlations turn out to be instrumental to enhance the efficiency which opens new ways for optimal control techniques. OPEN ACCESS RECEIVED

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