9 research outputs found
An implanter with a mixed ion beam for modifying the properties of the surface of construction materials
Analysis of the Role of Topography in the Spatial Differentiation of Landscapes Using Geoinformation and Statistical Methods
Who discovered the magnetocaloric effect?:Warburg, Weiss, and the connection between magnetism and heat
A magnetic body changes its thermal state when subjected to a changing magnetic field. In
particular, if done under adiabatic conditions, its temperature changes. For the past 15
years the magnetocaloric effect has been the focus of significant research due to its
possible application for efficient refrigeration near room temperature. At the same time,
it has become common knowledge within the magnetic refrigeration research community that
the magnetocaloric effect was discovered by the German physicist E. Warburg in 1881. We
re-examine the original literature and show that this is a misleading reading of what
Warburg did, and we argue that the discovery of the effect should instead be attributed to
P. Weiss and A. Piccard in 1917
Thermodynamics of the frustrated J1-J2 Heisenberg ferromagnet on the body-centered cubic lattice with arbitrary spin
Cooperative Jahn-Teller effect in a 2D mesoscopic C
Fullerene molecules adsorbed on surfaces often show macroscopic average distortions. As
charged ions C60n- are known to be Jahn-Teller (JT)
active, it is suggested that these distortions could be a manifestation of cooperative JT
effects (CJTE) due to interactions between neighbouring fullerene ions. In order to
understand the distortion properties it is necessary to take correlations between
different distortions into account. However, this canât easily be done in the mean field
approximation usually used to describe the CJTE. We therefore propose an alternative
procedure to describe 2D mesoscopic islands of C60 ions in which a pseudo
vector spin \hbox{} is evoked to represent degenerate JT-distorted states when the quadratic
JT coupling is considered. This approach is analogous to methods used for 2D magnetic
systems. We then use the differential operator technique in effective field theory within
the Ising approach. We include the effects of weak surface interactions and dynamic motion
between equivalent distortions via terms equivalent to anisotropy and a transverse field
in magnetism respectively. For distortions to
D5d symmetry, we determine single site
correlations as a function of temperature, the macroscopic average distortion describing a
structural phase transition, and the isothermal response function. Phase diagrams are
presented for relevant cases of the system parameters