41 research outputs found
Europium cyclooctatetraene nanowire carpets: A low-dimensional, organometallic, and ferromagnetic insulator
We investigate the magnetic and electronic properties of europium cyclooctatetraene (EuCot) nanowires by means of low-temperature X-ray magnetic circular dichroism (XMCD) and scanning tunneling microscopy (STM) and spectroscopy (STS). The EuCot nanowires are prepared in situ on a graphene surface. STS measurements identify EuCot as an insulator with a minority band gap of 2.3 eV. By means of Eu M5,4 edge XMCD, orbital and spin magnetic moments of (−0.1 ± 0.3)μB and (+7.0 ± 0.6)μB, respectively, were determined. Field-dependent measurements of the XMCD signal at the Eu M5 edge show hysteresis for grazing X-ray incidence at 5 K, thus confirming EuCot as a ferromagnetic material. Our density functional theory calculations reproduce the experimentally observed minority band gap. Modeling the experimental results theoretically, we find that the effective interatomic exchange interaction between Eu atoms is on the order of millielectronvolts, that magnetocrystalline anisotropy energy is roughly half as big, and that dipolar energy is approximately ten times lower
Influence of non-local damping on magnon properties of ferromagnets
We study the influence of non-local damping on magnon properties of Fe, Co,
Ni and FeCo () alloys. The Gilbert damping parameter
is typically considered as a local scalar both in experiment and in theoretical
modelling. However, recent works have revealed that Gilbert damping is a
non-local quantity that allows for energy dissipation between atomic sites.
With the Gilbert damping parameters calculated from a state-of-the-art
real-space electronic structure method, magnon lifetimes are evaluated from
spin dynamics and linear response, where a good agreement is found between
these two methods. It is found that non-local damping affects the magnon
lifetimes in different ways depending on the system. Specifically, we find that
in Fe, Co, and Ni the non-local damping decreases the magnon lifetimes, while
in and FeCo an opposite, non-local damping
effect is observed, and our data show that it is much stronger in the former
Tunable and robust room-temperature magnon-magnon entanglement
Although challenging, realizing controllable high-temperature entanglement is
of immense importance for practical applications as well as for fundamental
research in quantum technologies. Here, we report the existence of entangled
steady states in bipartite quantum magnonic systems at high temperatures. We
consider dissipative dynamics of two magnons in a bipartite antiferromagnet or
ferrimagnet subjected to a vibrational phonon mode and an external rotating
magnetic field. To quantify the bipartite magnon-magnon entanglement, we use
the entanglement negativity and compute its dependence on the temperature and
magnetic field. We show that, for any given phonon frequency and magnon-phonon
coupling rates, there are always ranges of the magnetic field amplitudes and
frequencies, for which bipartite magnon-magnon entanglement persists up to and
above the room temperature. The generality of the result allows for
experimental observation in a variety of crystals and synthetic bipartite
antiferromagnetic and ferrimagnetic materials.Comment: 6 pages, 5 figure