11 research outputs found
On Statistical Mechanics Developments of Clan Concept in Multiparticle Production
Clan concept has been introduced in multiparticle dynamics in order to
interpret the wide occurrence of negative binomial (NB) regularity in n-charged
particle multiplicity distributions (MDs) in various high energy collisions.
The centrality of clan concept led to the attempt to justify its occurrence
within a statistical model of clan formation and evolution. In this framework
all thermodynamical potentials have been explicitly calculated in terms of NB
parameters. Interestingly it was found that NB parameter k corresponds to the
one particle canonical partition function. The goal of this paper is to explore
a possible temperature and volume dependence of parameter k in various classes
of events in high energy hadron-hadron collisions. It is shown that the
existence of a phase transition at parton level from the ideal clan gas
associated to the semihard component with k>1 to the ideal clan gas of the hard
component with k<1 implies a discontinuity in the average number of particles
at hadron level.Comment: 20 pages, latex, no figures; v2: the description of the framework has
been considerably expanded, and the main body has been reorganized for
clarit
Monte Carlo investigation of the magnetic anisotropy in Fe/Dy multilayers
By Monte Carlo simulations in the canonical ensemble, we have studied the
magnetic anisotropy in Fe/Dy amorphous multilayers. This work has been
motivated by experimental results which show a clear correlation between the
magnetic perpendicular anisotropy and the substrate temperature during
elaboration of the samples. Our aim is to relate macroscopic magnetic
properties of the multilayers to their structure, more precisely their
concentration profile. Our model is based on concentration dependent exchange
interactions and spin values, on random magnetic anisotropy and on the
existence of locally ordered clusters that leads to a perpendicular
magnetisation. Our results evidence that a compensation point occurs in the
case of an abrupt concentration profile. Moreover, an increase of the
noncollinearity of the atomic moments has been evidenced when the Dy anisotropy
constant value grows. We have also shown the existence of inhomogeneous
magnetisation profiles along the samples which are related to the concentration
profiles
Magnetisation switching in a ferromagnetic Heisenberg nanoparticle with uniaxial anisotropy: A Monte Carlo investigation
We investigate the thermal activated magnetisation reversal in a single
ferromagnetic nanoparticle with uniaxial anisotropy using Monte Carlo
simulations. The aim of this work is to reproduce the reversal magnetisation by
uniform rotation at very low temperature in the high energy barrier hypothesis,
that is to realize the N\'eel-Brown model. For this purpose we have considered
a simple cubic nanoparticle where each site is occupied by a classical
Heisenberg spin. The Hamiltonian is the sum of an exchange interaction term, a
single-ion anisotropy term and a Zeeman interaction term. Our numerical data of
the thermal variation of the switching field are compared to an approximated
expression and previous experimental results on Co nanoparticles