44 research outputs found
The influence of multiple logics on the work of sustainability professionals
Organizational aspects, rather than technological ones, often represent the greatest barrier in the transition toward sustainable construction. However, despite sustainability professionals’ recognized role in sustainable development, few studies have focused on such professionals’ work. To understand the intrinsic influence of multiple institutional logics on the work and agency of sustainability professionals, we conducted 31 semi-structured interviews with sustainability professionals in Sweden’s construction industry. Building on the theoretical framework of institutional logics, the findings show how sustainability professionals’ everyday work, depending on the work conditions, is a blend of thankless, rewarding collaborative, and visionary work. In the organizational context of sustainable construction, characterized by dynamism and ambiguity, different institutional logics are combined in different ways to respond to shifting demands and problems. To maintain agency, sustainability professionals need to shift and balance their work depending on which logics are temporarily central. Showcasing how professionals cope with institutional contexts defined by multiple logics, the paper highlights the complexity involved in managing the vastness and ambiguity of sustainability and how it requires individuals to be both flexible and sensitive to the existence of multiple logics in their immediate context
A method for atomistic spin dynamics simulations: implementation and examples
We present a method for performing atomistic spin dynamic simulations. A
comprehensive summary of all pertinent details for performing the simulations
such as equations of motions, models for including temperature, methods of
extracting data and numerical schemes for performing the simulations is given.
The method can be applied in a first principles mode, where all interatomic
exchange is calculated self-consistently, or it can be applied with frozen
parameters estimated from experiments or calculated for a fixed
spin-configuration. Areas of potential applications to different magnetic
questions are also discussed. The method is finally applied to one situation
where the macrospin model breaks down; magnetic switching in ultra strong
fields.Comment: 14 pages, 19 figure
Spin relaxation signature of colossal magnetic anisotropy in platinum atomic chains
Recent experimental data demonstrate emerging magnetic order in platinum
atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy
-- colossal magnetic anisotropy (CMA) -- was earlier predicted to exist in
atomically thin platinum nanowires. Using spin dynamics simulations based on
first-principles calculations, we here explore the spin dynamics of atomically
thin platinum wires to reveal the spin relaxation signature of colossal
magnetic anisotropy, comparing it with other types of anisotropy such as
uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin
relaxation process distinctly and, most importantly, causes a large speed-up of
the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic
behavior of the nanowire exhibiting CMA should be possible to identify
experimentally at the nanosecond time scale for temperatures below 5 K. This
time-scale is accessible in e.g., soft x-ray free electron laser experiments.Comment: 9 pages, 3 figure
Atomistic spin dynamics of the CuMn spin glass alloy
We demonstrate the use of Langevin spin dynamics for studying dynamical
properties of an archetypical spin glass system. Simulations are performed on
CuMn (20% Mn) where we study the relaxation that follows a sudden quench of the
system to the low temperature phase. The system is modeled by a Heisenberg
Hamiltonian where the Heisenberg interaction parameters are calculated by means
of first-principles density functional theory. Simulations are performed by
numerically solving the Langevin equations of motion for the atomic spins. It
is shown that dynamics is governed, to a large degree, by the damping parameter
in the equations of motion and the system size. For large damping and large
system sizes we observe the typical aging regime.Comment: 18 pages, 9 figure
Microscopic Theory for Coupled Atomistic Magnetization and Lattice Dynamics
A coupled atomistic spin and lattice dynamics approach is developed which
merges the dynamics of these two degrees of freedom into a single set of
coupled equations of motion. The underlying microscopic model comprises local
exchange interactions between the electron spin and magnetic moment and the
local couplings between the electronic charge and lattice displacements. An
effective action for the spin and lattice variables is constructed in which the
interactions among the spin and lattice components are determined by the
underlying electronic structure. In this way, expressions are obtained for the
electronically mediated couplings between the spin and lattice degrees of
freedom, besides the well known inter-atomic force constants and spin-spin
interactions. These former susceptibilities provide an atomistic ab initio
description for the coupled spin and lattice dynamics. It is important to
notice that this theory is strictly bilinear in the spin and lattice variables
and provides a minimal model for the coupled dynamics of these subsystems and
that the two subsystems are treated on the same footing. Questions concerning
time-reversal and inversion symmetry are rigorously addressed and it is shown
how these aspects are absorbed in the tensor structure of the interaction
fields. By means of these results regarding the spin-lattice coupling, simple
explanations of ionic dimerization in double anti-ferromagnetic materials, as
well as, charge density waves induced by a non-uniform spin structure are
given. In the final parts, a set of coupled equations of motion for the
combined spin and lattice dynamics are constructed, which subsequently can be
reduced to a form which is analogous to the Landau-Lifshitz-Gilbert equations
for spin dynamics and damped driven mechanical oscillator for the ...Comment: 22 pages, including 7 pages of Appendix and references, 6 figure
A theoretical analysis of inertia-like switching in magnets: applications to a synthetic antiferromagnet
The magnetization dynamics of a synthetic antiferromagnet subject to a short
magnetic field pulse, has been studied by using a combination of
first-principles and atomistic spin dynamics simulations. We observe switching
phenomena on the time scale of tens of picoseconds, and inertia-like behavior
in the magnetization dynamics. We explain the latter in terms of a dynamic
redistribution of magnetic energy from the applied field pulse to other
possible energy terms, such as the exchange interaction and the magnetic
anisotropy, without invoking concepts such as inertia of an antiferromagnetic
vector. We also demonstrate that such dynamics can also be observed in a
ferromagnetic material where the incident field pulse pumps energy to the
magnetic anisotropy
Dynamics of diluted magnetic semiconductors from atomistic spin dynamics simulations: Mn doped GaAs as a case study
The dynamical behavior of the magnetism of diluted magnetic semiconductors
(DMS) has been investigated by means of atomistic spin dynamics simulations.
The conclusions drawn from the study are argued to be general for DMS systems
in the low concentration limit, although all simulations are done for 5%
Mn-doped GaAs with various concentrations of As antisite defects. The
magnetization curve, , and the Curie temperature have been
calculated, and are found to be in good correspondence to results from Monte
Carlo simulations and experiments. Furthermore, equilibrium and non-equilibrium
behavior of the magnetic pair correlation function have been extracted. The
dynamics of DMS systems reveals a substantial short ranged magnetic order even
at temperatures at or above the ordering temperature, with a non-vanishing pair
correlation function extending up to several atomic shells. For the high As
antisite concentrations the simulations show a short ranged anti-ferromagnetic
coupling, and a weakened long ranged ferromagnetic coupling. For sufficiently
large concentrations we do not observe any long ranged ferromagnetic
correlation. A typical dynamical response shows that starting from a random
orientation of moments, the spin-correlation develops very fast ( 1ps)
extending up to 15 atomic shells. Above 10 ps in the simulations, the
pair correlation is observed to extend over some 40 atomic shells. The
autocorrelation function has been calculated and compared with ferromagnets
like bcc Fe and spin-glass materials. We find no evidence in our simulations
for a spin-glass behaviour, for any concentration of As antisites. Instead the
magnetic response is better described as slow dynamics, at least when compared
to that of a regular ferromagnet like bcc Fe.Comment: 24 pages, 15 figure