Effect of interfacial modifications on magnetic, morphological and transport properties of CoFe/n-Si thin film structures using ion irradiation.

• Ion beam modification has been studied for CoFe/n-Si interfaces. • Ordered array of grains has been observed which is due to recrystallization phenomenon. • Drastic change in M-H loops from antiferromagnetic coupled phase to ferromagnetic phase has been observed. • A significant electronic transport has been observed with and without magnetic field. • Magneto-resistance of ∼7% has been estimated for the structure. Interfacial structures of ferromagnetic (FM) metal combined with semiconductor (SC) are key step for realizing spintronic devices where spin degree of freedom can also be utilized in addition to the charge of electron. Tailoring of such interfaces (of FM/SC) is known to tune the magnetic, optical, structural and transport properties. Swift heavy ion irradiation (SHI) can be used as a potential tool to tailor the interfaces. In our present work, effect of ion beam irradiation (100 meV Ni+7 ions) on the CoFe/n-Si interfacial structures had been studied. Thin films of CoFe was deposited by electron beam evaporation technique using CoFe metallic alloy on Si substrate. The realized interfacial structure was characterized from structural, morphological and magnetic point of view. The surface exhibits grainy structure with very fine domain (∼50 nm) on the irradiation. Electronic transport study across the interface shows an increase in current on irradiation with significant magnetic field sensitivity and a magnetoresistance of ∼7% has been observed. The observed results of increased magnetization and enhanced magnetic field sensitivity has been understood in the realm of irradiation induced interfacial intermixing across the interfaces. The chemical phases formed and nature of the interface as a result of irradiation was probed by X-ray photoelectron spectroscopy (XPS) study which confirms the formation of various silicide phases along with the metallic phase. The results were also compared with our earlier studies [15–16] on CoFe/n-Si system and found that fluence of 1 × 1011 ions/cm2 seems significant to result in interesting magnetic and transport properties without much damage to interface. [ABSTRACT FROM AUTHOR]