Emergence of magnetic anisotropy by surface adsorption of transition metal dimers on γ-graphyne framework

Abstract

In this paper a systematic study is carried out to demonstrate the structural stability and magnetic novelty of adsorbing transition metal (TM) dimers (A-B) on graphyne (GY) surface, GY@A-B. Our research points out that the dimers are strongly adsorbed onto GY due to their large natural pores and the electron affinity of the sp-hybridized carbon atoms. Electronic properties of these dimer-graphyne composite systems are of particular importance as they behave as degenerate semiconductors with partial occupation of states at E F. Furthermore, their remarkable spin polarization (>80%) at Fermi energy (E F) can be of paramount importance in spintronics applications. Most of the GY@A-B structures exhibit large magnetic anisotropies as well as magnetic moments along the out-of-plane direction with respect to the GY surface. Particularly, GY@Co–Ir, GY@Ir–Ir and GY@Ir–Os structures possess positive magnetic anisotropic energies (MAE) of 121 meV, 81 meV and 137 meV, respectively, which are comparable to other well-known TM dimer doped systems. The emergence of high MAE can be understood using the second-order perturbation theory on the basis of the strong spin–orbit coupling (SOC) between the two TMs and the degeneracy of their d-orbitals near E F. A close correspondence between the simulated and the analytical results has been established through our work. Further, a simple estimation shows that, GY@A-B structures have the potential to store data up to 64 PB m−2. These intriguing electronic characteristics along with magnetism suggest GY@A-B to be a promising material for future magnetic storage devices.

Tuning the magnetic anisotropy energy by external electric fields of CoPt dimers deposited on graphene

“…For this reason, the manipulation of the MAE of atomic-scale TM-based systems still remains the subject of intense research activity from both fundamental and technological perspectives. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] For example, tailoring the MAE by varying sample-parameters such as substrate, overlayer capping, TM-alloying, etc., [11][12][13][14][15][16][17][18][19][20] has open the possibility of new directions on the quantum material designs. In addition, the importance of controlling the magneto-anisotropic properties by external parameters such as laser-fields, polarized currents, and external electric fields has also been the target of many studies.…”

“…In addition, the importance of controlling the magneto-anisotropic properties by external parameters such as laser-fields, polarized currents, and external electric fields has also been the target of many studies. [5][6][7][8][9][10][11]13,17,19,[21][22][23][24][25][26][27] The control of the MAE by external static electric fields appears to be more appropriate due to their local character, 28 reversibility, energetically competitive characteristics, and more importantly, it would avoid the heating of the sample by dissipative and resistive effects. 29 Hence, one may conclude that an ideal nanomagnet should have a large MAE, and at the same time, it should be susceptible to an EF, which can induce magnetization reversal or at least reduce the energy barrier at relatively small EFs.…”

“…Recently, intense research activity has been devoted in the direction of using external electric fields to control or tailor the magnetic properties of deposited small clusters. [5][6][7][8][9][10][11]13 For instance, it was experimentally shown that the direction of the magnetization of Fe/Mo(110) could be switched upon applying an external EF generated by a tip of a scanning tunneling microscope. 13 From the theoretical point of view, studies on adatoms and dimers deposited on graphene have shown that magnetism can be very sensitive to EFs.…”

“…13 From the theoretical point of view, studies on adatoms and dimers deposited on graphene have shown that magnetism can be very sensitive to EFs. [5][6][7][8][9][10][11]27 The singular electronic structure of graphene, [30][31][32] with its linear dispersion relation and its high-room-temperature carrier mobility, 31 weak spin-orbit and hyperfine interactions, 33 manageable growth, and a long spin-lifetime 34 would indeed favor magnetic stability. For instance, by using density functional theory (DFT) and the torque method 35 for the calculations of the MAE, Hu et al, 9 have shown that bimetallic Pt-Ir and Os-Ru dimers deposited on graphene with defects could develop colossal MAEs between 60-85 meV, which can be manipulated to some extent through electric fields.…”

“…For this reason, the manipulation of the MAE of atomic-scale TM-based systems still remains the subject of intense research activity from both fundamental and technological perspectives. 5–20 For example, tailoring the MAE by varying sample-parameters such as substrate, overlayer capping, TM-alloying, etc. , 11–20 has open the possibility of new directions on the quantum material designs.…”