Graphene nanoflakes in external electric and magnetic in-plane fields

TL;DR

This study investigates how external in-plane electric and magnetic fields influence the spin states and magnetic ordering of graphene nanostructures, revealing diverse spin configurations and magnetic behaviors.

Contribution

It provides a detailed analysis of spin phase diagrams of graphene nanoflakes under external fields using the Hubbard model and Mean Field Approximation, highlighting new magnetic phenomena.

Findings

Identification of various nonzero spin states and their stability ranges.

Prediction of antiferromagnetic orderings in zero-spin phases.

Opposite effects of electric fields on magnetization at different magnetic field strengths.

Abstract

The paper discusses the influence of the external in-plane electric and magnetic field on the ground state spin phase diagram of selected monolayer graphene nanostructures. The calculations are performed for triangular graphene nanoflakes with armchair edges as well as for short pieces of armchair graphene nanoribbons with zigzag terminations. The Mean Field Approximation (MFA) is employed to solve the Hubbard model. The total spin for both classes of nanostructures is discussed as a function of external fields for various structure sizes, for charge neutrality conditions as well as for weak charge doping. The variety of nonzero spin states is found and their stability ranges are determined. For some structures, the presence of antiferromagnetic orderings is predicted within the zero-spin phase. The process of magnetization of nanoflakes with magnetic field at constant electric field is also investigated, showing opposite effect of electric field at low and at high magnetic fields.