Abstract
Recent experimental studies proved the presence of the triplet spin state in atomically precise heptauthrene nanostructure of nanographene type (composed of two interconnected triangles with zigzag edge). In the paper, we report the computational study predicting the possibility of controlling this spin state with an external in-plane electric field by causing the spin switching. We construct and discuss the ground state magnetic phase diagram involving (triplet) state, antiferromagnetic state and non-magnetic state and predict the switching possibility with the critical electric field of the order of 0.1 V/Å. We discuss the spin distribution across the nanostructure, finding its concentration along the longest zigzag edge. To model our system of interest, we use the mean-field Hubbard Hamiltonian, taking into account the in-plane external electric field as well as the in-plane magnetic field (in a form of the exchange field from the substrate). We also assess the effect of uniaxial strain on the magnetic phase diagram.
Highlights
Electric field control of magnetism lies at heart of the developing spintronics [1].For this purpose, a variety of materials and a wide range of physical mechanisms have been employed [1,2,3,4], with emphasis put on the nanostructures
It might be mentioned first that the Hubbard model in mean-field approximation has been used in Ref. [69] to simulate the density of states distribution across the heptauthrene nanostructure, which has been successfully compared with the results of scanning tunneling microscopy experiment
Let us comment that the parameter ∆ which we introduce in our theoretical model to account for the spin-dependent energy splitting can originate not from the external magnetic field itself but primarily from the exchange field coming from the ferromagnetic substrate
Summary
Electric field control of magnetism lies at heart of the developing spintronics [1].For this purpose, a variety of materials and a wide range of physical mechanisms have been employed [1,2,3,4], with emphasis put on the nanostructures. In addition to the unique properties of two-dimensional graphene sheets, various forms of nanographenes (graphene nanoflakes), being polyaromatic hydrocarbons [11,12,13,14], constitute potentially promising candidates for the applications in the field of spintronics. Such systems, at the cross-section of physics and chemistry, combine the advantages of molecular systems (such as a chemical route to synthesis of fully reproducible nanostructures) and the unique properties and potential of graphene. The presence of edge in nanographene offers an additional possibility of modifying a wide range of its properties to reach the desired behaviour
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