Controlling magnetism on metal surfaces with non-magnetic means: electric fields and surface charging

Abstract

We review the state of the art of surface magnetic property control with non-magnetic means, concentrating on metallic surfaces and techniques such as charge-doping or external electric field (EEF) application. Magneto-electric coupling via EEF-based charge manipulation is discussed as a way to tailor single adatom spins, exchange interaction between adsorbates or anisotropies of layered systems. The mechanisms of paramagnetic and spin-dependent electric field screening and the effect thereof on surface magnetism are discussed in the framework of theoretical and experimental studies. The possibility to enhance the effect of EEF by immersing the target system into an electrolyte or ionic liquid is discussed by the example of substitutional impurities and metallic alloy multilayers. A similar physics is pointed out for the case of charge traps, metallic systems decoupled from a bulk electron bath. In that case the charging provides the charge carrier density changes necessary to affect the magnetic moments and anisotropies in the system. Finally, the option of using quasi-free electrons rather than localized atomic spins for surface magnetism control is discussed with the example of Shockley-type metallic surface states confined to magnetic nanoislands.

Effective gating and tunable magnetic proximity effects in two-dimensional heterostructures

“…Even the simple effect of electrostatic screening in a metal is intrinsically quantum mechanical, as it is apparent from the spin-dependent screening in F, 31,32 shown in Fig. 2 for a Co slab.…”

Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

“…Whereas, a reduced variation of the spatial charge is also observed underneath the surface. Such charge re- distribution can even be spin-dependent which can alter the magnetic order 13,15 . Meanwhile, the exchange interaction across the coupling medium in Fe/Cu N /Fe trilayer, supported on a Pt(001) substrate, determines the magnetic state to be either ferromagnetic (FM) or antiferromagnetic (AF).…”

“…Recently a more efficient method has been revealed, on the basis of magnetoelectric coupling, for tuning the spin alignment in a ferromagnet (FM) by both Density Functional theory [12][13][14][15][16] and experimental studies 1,17,18 . For instance, the anisotropy properties of 2D ferromagnet could be tuned either by varying its intrinsic charge carriers 12,15 or the oxidation state by electric means 19 .…”

Tuning the magnetic anisotropy in single-layer crystal structures

“…Therefore, looking for materials with large MA is of importance for spintronics applications [7] and data storage [17]. Recent studies have shown that the magnetic moment and the MA in monolayer and bulk materials can be induced, modified, and tuned using an electric field (E field) [18][19][20][21], surface charging [22][23][24][25], applying biaxial strain [26][27][28][29], doping transition metal and other atoms [30,31], and dimers [32,33].…”