Tuning the tunneling magnetoresistance by using fluorinated graphene in graphene based magnetic junctions

Abstract

Spin polarized properties of fluorinated graphene as tunnel barrier with CrO2 as two HMF electrodes are studied using first principle methods based on density functional theory. Fluorinated graphene with different fluorine coverages is explored as tunnel barriers in magnetic tunnel junctions. Density functional computation for different fluorine coverages imply that with increase in fluorine coverages, there is increase in band gap (Eg) of graphene, Eg ∼ 3.466 e V was observed when graphene sheet is fluorine adsorbed on both-side with 100% coverage (CF). The results of CF graphene are compared with C4F (fluorination on one-side of graphene sheet with 25% coverage) and out-of-plane graphene based magnetic tunnel junctions. On comparison of the results it is observed that CF graphene based structure offers high TMR ∼100%, and the transport of carrier is through tunneling as there are no transmission states near Fermi level. This suggests that graphene sheet with both-side fluorination with 100% coverages acts as a perfect insulator and hence a better barrier to the carriers which is due to negligible spin down current (I↓) in both Parallel Configuration (PC) and Antiparallel Configuration (APC).

Graphene-based Symmetric and Non-Symmetric Magnetoresistive Junctions

“…Previous reports on MTJs using Gr spacer region are mostly limited to symmetric junctions in which both electrodes are the same material [15][16][17][18][19] . Our investigation includes symmetric junctions, both electrodes are Ni, and non-symmetric junctions, one is Ni and the other is Co and Gr monolayer (ML) is used as covalently bonded spacer.…”

“…Second, the electronic states of Gr at the Fermi level are mainly located at high symmetry K point in reciprocal space, 3 while only minority-spin states of Ni(111) and Co(111) exist at the K point [16][17][18] , which gives rise to a high TMR ratio.…”

CrO2-based heterostructure and magnetic tunnel junction: perfect spin filtering effect, spin diode effect and high tunnel magnetoresistance

“…[17][18][19][20] For the spintronic applications, there have been some studies on electronic transport properties based on CrO 2 electrode. [21][22][23][24][25][26] Meena and Choudhary [21][22][23][24][25] systemically investigated the spin transport properties for some magnetic tunnel junctions (MTJs) based on CrO 2 electrode and different barriers such as the graphene and the carbon nanotube, and large tunneling magnetoresistance (TMR) ratios were predicted. Leo et al 26 experimentally studied the TMR in the MTJ of CrO 2 /MgO/ CoFe (100), and revealed that the TMR sign can be reversed simply by subtle modications to the CrO 2 /MgO interface.…”