Patrik Henelius

Quantum Monte Carlo simulation of thin magnetic films

The stochastic series expansion quantum Monte Carlo method is used to study thin ferromagnetic films, described by a Heisenberg model including local anisotropies. The magnetization curve is calculated, and the results compared to Schwinger boson and many-body Greens function calculations. A transverse field is introduced in order to study the reorientation effect, in which the magnetization changes from out of plane to in plane. Since the approximate theoretical approaches above differ significantly from each other, and the Monte Carlo method is free of systematic errors, the calculation provides an unbiased check of the approximate treatments. By studying quantum spin models with local anisotropies, varying spin size, and a transverse field, we also demonstrate the general applicability of the recent cluster-loop formulation of the stochastic series expansion quantum Monte Carlo method.

Sign problem in Monte Carlo simulations of frustrated quantum spin systems

We discuss the: sign problem arising in Monte Carlo simulations of frustrated quantum spin systems. We show that for a class of semifrustrated systems [Heisenberg models with ferromagnetic coupling ...

Low-temperature properties of the dilute dipolar magnet LiHoxY1-xF4

We analyze recent experiments on the dilute rare-earth compound LiHoxY1-xF4 in the context of an effective Ising dipolar model. Using a Monte Carlo method we calculate the low-temperature behavior ...

Monte Carlo study of a two-dimensional quantum ferromagnet

We present quantum Monte Carlo results for the field and temperature dependence of the magnetization and the spin lattice relaxation rate

Theory of the magnetic phase diagram of Li Ho F 4

{1/T}_{1}

Collective Phenomena in the LiHoxY1?xF4 Quantum Ising Magnet: Recent Progress and Open Questions

of a two-dimensional

Ground state of the random-bond spin-1 Heisenberg chain

S=1/2

Theory of the magnetic phase diagram of LiHoF4

quantum Heisenberg ferromagnet. The Monte Carlo method, which yields results free of systematic errors, is described in detail. The high accuracy of the calculated magnetization allows for stringent tests of recent approximate analytical calculations. We also compare our results with recent experimental data for a

Local-density approximation for confined bosons in an optical lattice

\ensuremath{\nu}=1

Unreachable glass transition in dilute dipolar magnet

quantum Hall ferromagnet, which is expected to be well described by the Heisenberg model. The dynamic response function needed to extract