The diamagnetic phase transition in Magnetars

TL;DR

This paper explores the diamagnetic phase transition in magnetars, linking magnetic domain formation and oscillations to observable phenomena like bursts and crustal fractures, advancing understanding of magnetar magnetic behavior.

Contribution

It introduces a detailed theoretical framework connecting diamagnetic phase transition and magnetic domain dynamics to magnetar emissions and crustal activity.

Findings

Magnetic domain formation can cause observable magnetic oscillations.

Depinning of domain walls may trigger magnetar bursts.

Hall effect-driven domain wall motion is dissipative and influences magnetar activity.

Abstract

Neutron stars are ideal astrophysical laboratories for testing theories of the de Haas-van Alphen (dHvA) effect and diamagnetic phase transition which is associated with magnetic domain formation. The "magnetic interaction" between delocalized magnetic moments of electrons (the Shoenberg effect), can result in an effect of the diamagnetic phase transition into domains of alternating magnetization (Condon's domains). Associated with the domain formation are prominent magnetic field oscillation and anisotropic magnetic stress which may be large enough to fracture the crust of magnetar with a super-strong field. Even if the fracture is impossible as in "low-field" magnetar, the depinning phase transition of domain wall motion driven by low field rate (mainly due to the Hall effect) in the randomly perturbed crust can result in a catastrophically variation of magnetic field. This intermittent motion, similar to the avalanche process, makes the Hall effect be dissipative. These qualitative consequences about magnetized electron gas are consistent with observations of magnetar emission, and especially the threshold critical dynamics of driven domain wall can partially overcome the difficulties of "low-field" magnetar bursts and the heating mechanism of transient, or "outbursting" magnetar.