Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism.

The magnetism of DySc 2 N@C 80 endofullerene was studied with X-ray magnetic circular dichroism (XMCD) and a magnetometer with a superconducting quantum interference device (SQUID) down to temperatures of 2 K and in fields up to 7 T. XMCD shows hysteresis of the 4f spin and orbital moment in Dy III ions. SQUID magnetometry indicates hysteresis below 6 K, while thermal and nonthermal relaxation is observed. Dilution of DySc 2 N@C 80 samples with C 60 increases the zero-field 4f electron relaxation time at 2 K to several hours. I ncorporation of magnetic ions in molecular clusters can lead to the formation of so-called single-molecule magnets (SMMs).1 These molecules are characterized by slow magnetic relaxation, making them candidates for applications in quantum computing, spintronics, and high-density storage devices. Investigations on the magnetism of single ions inside fullerenes started with Gd@C 82 , which turned out to be paramagnetic down to 3 K. 9a For Dy@C 82 , superconducting quantum interference device (SQUID) and X-ray magnetic circular dichroism (XMCD) measurements revealed paramagnetic behavior down to 1.8 K.9b−e The observed magnetic moment is reduced in this system compared to the free trivalent Dy ion, which is attributed to a quenched orbital moment due to the crystal field splitting from the carbon cage and/or electron back-donation from the cage to the Dy ion. In contrast, C 80 NCFs have a carbon cage with a closed shell, and less coupling between the moments of the metal ions and a diamagnetic cage is expected. SQUID magnetization measurements on Ln 3 N@C 80 (Ln = Tb and Ho) 10a,b are in line with a model where the LF of the N 3− ion induces an easy axis for the individual Ln III moments directed along the respective Ln−N bond. In this model the magnetic anisotropy due to the LF is strong enough that the Ln III moments do not align with the external field but instead parallel to the bond directions. ) and Er x Sc 3−x N@ C 80 10d (x = 1, 2) above 1.8 K showed paramagnetism without hysteresis.In the present case we have a single Dy III ion in a diamagnetic carbon cage (see Figure 1). Since Sc III ions are not paramagnetic, the LF due to the N 3− ion will result in magnetic anisotropy directed along the Dy−N bond. Furthermore, if the LF stabilizes a ground state with a large J z , the prerequisite for magnetic bistability is fulfilled.

Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials' engineering tool in today's semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO3 at the interface between LaAlO3 and SrTiO3 oxides. Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO3 layer (TFM = 6-8 K) and is due to the exchange interaction between the magnetic moments of Eu-4f and of Ti-3d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin-orbit coupling in the same q2DES makes the LaAlO3/EuTiO3/SrTiO3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr.For further information see http://journals.iucr.org/services/authorrights.html Synchrotron radiation research is rapidly expanding with many new sources of radiation being created globally. Synchrotron radiation plays a leading role in pure science and in emerging technologies. The Journal of Synchrotron Radiation provides comprehensive coverage of the entire field of synchrotron radiation research including instrumentation, theory, computing and scientific applications in areas such as biology, nanoscience and materials science. Rapid publication ensures an up-to-date information resource for scientists and engineers in the field.Crystallography Journals Online is available from journals.iucr.org J. Synchrotron Rad. (2012 X-Treme is a soft X-ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with É cole Polytechnique Fé dé rale de Lausanne. The beamline is dedicated to polarization-dependent X-ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end-station has a superconducting 7 T-2 T vector magnet, with sample temperature down to 2 K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 Â 10 12 photons s À1, are presented. Scientific examples showing X-ray magnetic circular and X-ray magnetic linear dichroism measurements are also presented.

Possible ferromagnetism induced in otherwise nonmagnetic materials has been motivating intense research in complex oxide heterostructures. Here we show that a confined magnetism is realized at the interface between SrTiO3 and two insulating polar oxides, BiMnO3 and LaAlO3. By using polarization dependent x-ray absorption spectroscopy, we find that in both cases the magnetism can be stabilized by a negative exchange interaction between the electrons transferred to the interface and local magnetic moments. These local magnetic moments are associated with magnetic Ti3+ ions at the interface itself for LaAlO3/SrTiO3 and to Mn3+ ions in the overlayer for BiMnO3/SrTiO3. In LaAlO3/SrTiO3 the induced magnetism is quenched by annealing in oxygen, suggesting a decisive role of oxygen vacancies in this phenomenon.