Lutetium-doped EuO films grown by molecular-beam epitaxy

Abstract

The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

Epitaxial growth of europium monoxide on diamond

“…At 5 K, the EuO grown on the epitaxial diamond film has a maximum magnetization at 30 000 G of 3.7 6 0.1 l B per europium ion. These values are considerably lower than the 6.9 l B per europium ion found in bulk EuO and in high-quality EuO epitaxial films, 8,9,17,28,33,39 and is indicative of our films on diamond not yet being the quality of epitaxial EuO films grown on YAlO 3 , 8,33 LuAlO 3 , 29 Si, 8 and GaAs. 28 In summary, the epitaxial integration of ferromagnetic EuO on epitaxial diamond films and single-crystal diamond Magnetization as a function of temperature of (a) the same 25 nm thick EuO film grown on an epitaxial diamond film as shown in Fig.…”

“…12 The MIT and CMR occur around the Curie temperature (T C ), which is 69 K in bulk EuO. 13 T C can be enhanced dramatically by doping with trivalent cations 8,9,[14][15][16][17][18][19][20][21] or by introducing oxygen vacancies (EuO 1-x ). [22][23][24][25] Theorists predict that a T C of $200 K is possible by combining doping and compressive strain.…”

“…Europium oxide (EuO) is a ferromagnetic semiconductor with a spin-polarization of at least 96%, 8,9 giving it the second highest spin-polarization of all known materials after CrO 2 . 10 Furthermore, doped EuO has a metal-to-insulator transition (MIT) involving a change in resistivity of up to 13 orders of magnitude 11 and exhibits colossal magneto-resistance (CMR) up to 6 orders of magnitude.…”

Direct Epitaxial Integration of the Ferromagnetic Semiconductor EuO with Silicon for Spintronic Applications

“…Not only does doped EuO exhibit a spin polarization close to 100% due to enormous (~0.6 eV) spin splitting of its conduction band but also it can be conductance-matched with Si by doping with oxygen vacancies or trivalent rare-earth atoms such as Gd, La or Lu [18,[30][31][32][33]. Its Heisenberglike magnetism (7 μ B per Eu 2+ ion) arises from the half-filled 4f states which constitute the top of the valence band [33].…”

“…Its Heisenberglike magnetism (7 μ B per Eu 2+ ion) arises from the half-filled 4f states which constitute the top of the valence band [33]. Stoichiometric EuO has a low FM Curie temperature T c of about 69 K, but chemical doping and axial strain can increase T c significantly [32][33][34][35][36]. Its band gap of 1.12 eV matches that of Si [33].…”