Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. To control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin centre. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy.
Substrate surfaces terminated with a specific surface reconstruction are a prerequisite for the controlled epitaxial growth of most materials. Focusing on SrTiO3 (001) substrates, it has recently been shown that in situ substrate termination by thermal annealing has decisive advantages over standard termination methods. We report here that in situ substrate termination is a generally applicable method not restricted to SrTiO3 crystals. We specifically demonstrate the successful surface preparation of doped SrTiO3 (001), LaAlO3 (001), NdGaO3 (001), DyScO3 (110), TbScO3 (110), MgO (001), and Al2O3 (0001) surfaces.
We present the fabrication
and exploration of arrays of nanodots
of SrRuO
3
with dot sizes between 500 and 15 nm. Down to
the smallest dot size explored, the samples were found to be magnetic
with a maximum Curie temperature
T
C
achieved
by dots of 30 nm diameter. This peak in
T
C
is associated with a dot-size-induced relief of the epitaxial strain,
as evidenced by scanning transmission electron microscopy.
We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO
3
thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Grüneisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.
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