Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEpitaxial Zn(x)Fe(3-x)O(4) Thin Films: A Spintronic Material with Tunable Electrical and Magnetic Properties
378
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The ferrimagnetic spinel oxide Zn(x)Fe(3-x)O(4) combines high Curie temperature and spin polarization with tunable electrical and magnetic properties, making it a promising functional material for spintronic devices. We have grown epitaxial thin films with 0<=x<=0.9 on MgO(001) substrates with excellent structural properties both in pure Ar atmosphere and an Ar/O2 mixture by laser molecular beam epitaxy. We find that the electrical conductivity and the saturation magnetization can be tuned over a wide range during growth. Our extensive characterization of the films provides a clear picture of the underlying physics of this spinel ferrimagnet with antiparallel Fe moments on the A and B sublattice: (i) Zn substitution removes both Fe3+ moments from the A sublattice and itinerant charge carriers from the B sublattice, (ii) growth in finite oxygen partial pressure generates Fe vacancies on the B sublattice also removing itinerant charge carriers, and (iii) application of both Zn substitution and excess oxygen results in a compensation effect as Zn substitution partially removes the Fe vacancies. A decrease (increase) of charge carrier density results in a weakening (strengthening) of double exchange and thereby a decrease (increase) of conductivity and the saturation magnetization. This scenario is confirmed by the observation that the saturation magnetization scales with the longitudinal conductivity. The combination of tailored films with semiconductor materials such as ZnO in multi-functional heterostructures seems to be particularly appealing.
rate research
Read More
By means of photoemission and x-ray absorption spectroscopy, we have studied the electronic structure of (Ni,Zn,Fe,Ti)$_{3}$O$_{4}$ thin films, which exhibits a cluster glass behavior with a spin-freezing temperature $T_f$ of $sim 230$ K and photo-induced magnetization (PIM) below $T_f$. The Ni and Zn ions were found to be in the divalent states. Most of the Fe and Ti ions in the thin films were trivalent (Fe$^{3+}$) and tetravalent (Ti$^{4+}$), respectively. While Ti doping did not affect the valence states of the Ni and Zn ions, a small amount of Fe$^{2+}$ ions increased with Ti concentration, consistent with the proposed charge-transfer mechanism of PIM.
We investigated structural, magnetic and electrical properties of sputter deposited Mn-Fe-Ga compounds. The crystallinity of the Mn-Fe-Ga thin films was confirmed using x-ray diffraction. X-ray reflection and atomic force microscopy measurements were utilized to investigate the surface properties, roughness, thickness and density of the deposited Mn-Fe-Ga. Depending on the stoichiometry, as well as the used substrates (SrTiO3 (001) and MgO (001)) or buffer layer (TiN) the Mn-Fe-Ga crystallizes in the cubic or the tetragonally distorted phase. Anomalous Hall effect and alternating gradient magnetometry measurements confirmed strong perpendicular magnetocrystalline anisotropy. Low saturation magnetization and hard magnetic behavior was reached by tuning the composition. Temperature dependent anomalous Hall effect measurements in a closed cycle He-cryostat showed a slight increase in coercivity with decreasing temperature (300K to 2K). TiN buffered Mn2.7Fe0.3Ga revealed sharper switching of the magnetization compared to the unbuffered layers.
Magnetite epitaxial thin films have been prepared by pulsed laser deposition at 340 C on MgO and Si substrates. One key result is that the thin film properties are almost identical to the properties of bulk material. For 40 - 50 nm thick films, the saturation magnetization and conductivity are respectively 453 emu/cm^3 and 225 1/(Ohm cm) at room temperature. The Verwey transition is at 117 K. The Hall effect indicates an electron concentration corresponding to 0.22 electrons per formula unit at room temperature. Normal and anomalous Hall effect both have a negative sign.
The double perovskite Sr2CrReO6 is an interesting material for spintronics, showing ferrimagnetism up to 635 K with a predicted high spin polarization of about 86%. We fabricated Sr2CrReO6 epitaxial films by pulsed laser deposition on (001)-oriented SrTiO3 substrates. Phase-pure films with optimum crystallographic and magnetic properties were obtained by growing at a substrate temperature of 700 degree C in pure O2 of 6.6x10-4 mbar. The films are c-axis oriented, coherently strained, and show less than 20% anti-site defects. The magnetization curves reveal high saturation magnetization of 0.8 muB per formula unit and high coercivity of 1.1 T, as well as a strong magnetic anisotropy.
CaFe2O4 is a highly anisotropic antiferromagnet reported to display two spin arrangements with up-up-down-down (phase A) and up-down-up-down (phase B) configurations. The relative stability of these phases is ruled by the competing ferromagnetic and antiferromagnetic interactions between Fe3+ spins arranged in two different environments, but a complete understanding of the magnetic structure of this material does not exist yet. In this study we investigate epitaxial CaFe2O4 thin films grown on TiO2 (110) substrates by means of Pulsed Laser Deposition (PLD). Structural characterization reveals the coexistence of two out-of-plane crystal orientations and the formation of three in-plane oriented domains. The magnetic properties of the films, investigated macroscopically as well as locally, including highly sensitive Mossbauer spectroscopy, reveal the presence of just one order parameter showing long-range ordering below T = 185 K and the critical nature of the transition. In addition, a non-zero in-plane magnetization is found, consistent with the presence of uncompensated spins at phase or domain boundaries, as proposed for bulk samples.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
