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Magnetization jump in one dimensional J?-?Q 2 model with anisotropic exchange.

ABSTRACT: We investigate the adiabatic magnetization process of the one-dimensional J?-?Q 2 model with XXZ anisotropy g in an external magnetic field h by using density matrix renormalization group (DMRG) method. According to the characteristic of the magnetization curves, we draw a magnetization phase diagram consisting of four phases. For a fixed nonzero pair coupling Q, (i) when g < -1, the ground state is always ferromagnetic in spite of h; (ii) when g > -1 but still small, the whole magnetization curve is continuous and smooth; (iii) if further increasing g, there is a macroscopic magnetization jump from partially- to fully-polarized state; (iv) for a sufficiently large g, the magnetization jump is from non- to fully-polarized state. By examining the energy per magnon and the correlation function, we find that the origin of the magnetization jump is the condensation of magnons and the formation of magnetic domains. We also demonstrate that while the experienced states are Heisenberg-like without long-range order, all the jumped-over states have antiferromagnetic or Néel long-range orders, or their mixing.

SUBMITTER: Mao BB

PROVIDER: S-EPMC5741776 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Magnetization jump in one dimensional J - Q <sub>2</sub> model with anisotropic exchange.

Mao Bin-Bin BB Cheng Chen C Chen Fu-Zhou FZ Luo Hong-Gang HG

Scientific reports 20171222 1

We investigate the adiabatic magnetization process of the one-dimensional J - Q <sub>2</sub> model with XXZ anisotropy g in an external magnetic field h by using density matrix renormalization group (DMRG) method. According to the characteristic of the magnetization curves, we draw a magnetization phase diagram consisting of four phases. For a fixed nonzero pair coupling Q, (i) when g < -1, the ground state is always ferromagnetic in spite of h; (ii) when g > -1 but still small, the whole magnet ...[more]

PMID: 29273774

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Project description:PURPOSE:An extended phase graph framework (EPG-X) for modeling systems with exchange or magnetization transfer (MT) is proposed. THEORY:EPG-X models coupled two-compartment systems by describing each compartment with separate phase graphs that exchange during evolution periods. There are two variants: EPG-X(BM) for systems governed by the Bloch-McConnell equations, and EPG-X(MT) for the pulsed MT formalism. For the MT case, the "bound" protons have no transverse components, so their phase graph consists of only longitudinal states. METHODS:The EPG-X model was validated against steady-state solutions and isochromat-based simulation of gradient-echo sequences. Three additional test cases were investigated: (i) MT effects in multislice turbo spin-echo; (ii) variable flip angle gradient-echo imaging of the type used for MR fingerprinting; and (iii) water exchange in multi-echo spin-echo T2 relaxometry. RESULTS:EPG-X was validated successfully against isochromat based transient simulations and known steady-state solutions. EPG-X(MT) simulations matched in-vivo measurements of signal attenuation in white matter in multislice turbo spin-echo images. Magnetic resonance fingerprinting-style experiments with a bovine serum albumin (MT) phantom showed that the data were not consistent with a single-pool model, but EPG-X(MT) could be used to fit the data well. The EPG-X(BM) simulations of multi-echo spin-echo T2 relaxometry suggest that exchange could lead to an underestimation of the myelin-water fraction. CONCLUSIONS:The EPG-X framework can be used for modeling both steady-state and transient signal response of systems exhibiting exchange or MT. This may be particularly beneficial for relaxometry approaches that rely on characterizing transient rather than steady-state sequences. Magn Reson Med 80:767-779, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Dataset Information

Magnetization jump in one dimensional J?-?Q 2 model with anisotropic exchange.

Publications

Magnetization jump in one dimensional J - Q <sub>2</sub> model with anisotropic exchange.

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