| In this paper,a new type of manganese-doped zinc-arsenic-based Ⅱ-Ⅱ-Ⅴ diluted magnetic semiconductor(Ba,K)(Zn,Mn)2As2 thin films were successfully prepared for the first time by using pulsed laser deposition method.The growth method and the the research of various physical properties mainly includes the following parts:1.For the growth and research of thin films of air-sensitive materials,a comprehensive system which enables the whole process of pulsed laser deposition,X-ray diffraction,Hall bar photoetching,electrodes metal deposition,wire bonding,and low-temperature electrical transport measurement all performed in an environment protected which excludes the air was developed.2.Single-phased,single-oriented thin films of Mn-doped ZnAs-based diluted magnetic semiconductor(DMS)Ba1-xKx(Zn1-yMny)2As2(x=0.03,0.08;y=0.15)have been deposited on Si,SrTiO3,LaAlO3,(La,Sr)(Al,Ta)O3,and MgAl2O4 substrates,respectively.In comparison with films of x=0.03 which possess relatively higher resistivity,weaker magnetic performances,and larger energy gap,thin films of x=0.08 show better electric and magnetic performances.Strong magnetic anisotropy is found in films of x=0.08 grown on(La,Sr)(Al,Ta)O3 substrate with their magnetic polarization aligned almost solely on the film growth direction.Under the condition of obtaining high-quality DMS films,we successfully fabricated the heterojunction composed of epitaxial magnetic semiconductor films and epitaxial iron-based superconductor films with the same structure for the first time.3.Further measurements of magnetic and electrical transport properties of the Ba0.92K0.08(Zn0.85Mn0.15)2As2 thin films were performed in this work,and several results have been found.Firstly,there is a competition of long-range ferromagnetic order and short-range antiferromagnetic order in the thin films.Secondly,the conductivity of the thin film of x=0.08 conforms to the Mott variable range hopping law of conductivity,ln(σ)～T-1/4.Thirdly,the magnetic conductance is proportional to the square of the relative magnetization,and the proportionality factor is related to T-1/2.Fourthly,the source of the ferromagnetism of the film can be explained in this way,the hole carriers are in Anderson’s localized state,and Bound Magnetic Pole(BMP)state will be formed in the films as the presence of Mn2+ions.The long-range ferromagnetic is associated with the transition of carriers between BMPs.Lastly,through the comparison and analysis of the lattice constant and localization of the samples,we found that the increase in the inter-layer As atomic distance(di)caused by tensile stress may be the reason why the carriers in the film are more localized than these in the polycrystalline,and this change may make the Curie temperature of thin films in the same doping move to high temperature.4.Considering the influence of the magnetic signal of the single crystal substrate itself on the magnetic measurement of the magnetic thin film,we systematically studied the magnetic properties of a variety of single crystals such as perovskite oxides,magnesium oxide and silicon.The direct magnetic measurement showed that the magnetic signal of these single-crystals include three contributions,namely,intrinsic diamagnetic contribution,ferromagnetic contribution,and paramagnetic contribution due to magnetic impurities.Using the different characteristics of these above contributions,we got three kinds of magnetic contributions separately.Then,we analysed their influence on the magnetic measurement of a certain volume of magnetic thin film.It could be found that the paramagnetic contribution of the silicon single-crystal substrate has the lowest influence on the measurement,and a method of obtaining relatively accurate magnetic signal of thin films has been proposed from this.In addition,we discussed the change in the intrinsic diamagnetism with temperature,dχ/dT,of different single crystals,which are usually ignored in previous works. |
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