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Machine learning is changing how we design and interpret experiments in materials science. In this work we show how unsupervised learning, combined with ab initio random structure searching, improves our understanding of structural metastability in multicomponent alloys. We focus on the case of Al-O-N alloys where the formation of aluminum vacancies in wurtzite AlN upon the incorporation of substitutional oxygen can be seen as a general mechanism of solids where crystal symmetry is reduced to stabilize defects. The ideal AlN wurtzite crystal structure occupation cannot be matched due to the presence of an aliovalent hetero-element into the structure. The traditional interpretation of the c-lattice shrinkage in sputter-deposited Al-O-N films from X-ray diffraction (XRD) experiments suggests the existence of a solubility limit at 8 at.% oxygen content. Here we show that such naive interpretation is misleading. We support XRD data with accurate ab initio modeling and dimensionality reduction on advanced structural descriptors to map structure-property relationships. No signs of a possible solubility limit are found. Instead, the presence of a wide range of non-equilibrium oxygen-rich defective structures emerging at increasing oxygen contents suggests that the formation of grain boundaries is the most plausible mechanism responsible for the lattice shrinkage measured in Al-O-N sputtered films. We further confirm our hypothesis using positron annihilation lifetime spectroscopy.

Interfaces separating ferromagnetic (FM) layers from non-ferromagnetic layers offer unique properties due to spin-orbit coupling and symmetry breaking, yielding effects such as exchange bias, perpendicular magnetic anisotropy, spin-pumping, spin-transfer torques, conversion between charge and spin currents and vice-versa. These interfacial phenomena play crucial roles for magnetic data storage and transfer applications, which require forming FM nano-structures embedded in non-ferromagnetic matrices. Here, we investigate the possiblity of creating such nano-structures by ion-irradiation. We study the effect of lateral confinement on the ion-irradiation-induced reduction of non-magnetic metal oxides (e.g., antiferro- or paramagnetic) to ferromagnetic metals. Our findings are later exploited to form 3-dimensional magnetic interfaces between Co, CoO and Pt by spatially-selective irradiation of CoO/Pt multilayers. We demonstrate that the mechanical displacement of the O atoms plays a crucial role during their reduction from insulating, non-ferromagnetic Co oxides to metallic Co. Metallic Co yields both perpendicular magnetic anisotropy in the generated Co/Pt nano-structures, and, at low temperatures, exchange bias at vertical interfaces between Co and CoO. If pushed to the limit of ion-irradiation technology, this approach could, in principle, enable the creation of densely-packed, atomic scale ferromagnetic point-contact spin-torque oscillator (STO) networks, or conductive channels for current-conned-path based current perpendicular-to-plane giant magnetoresistance read-heads.

The demand on high data transfer and storage capacities requires smaller devices to transmit or save data. Forming well-defined ferromagnetic and electrically conducting volumes in a non-magnetic and insulating matrix in nanometer dimensions can pave a way to the production of such small devices. Oxygen reduction in Co3O4/Pd multilayers is possible by local proton irradiation resulting in ferromagnetic and conducting Co embedded in a nonmagnetic and insulating Co3O4 matrix [1]. To understand the mechanism behind this, we analysed in-plane single- and out-of-plane multilayer cobalt oxide films after H+ irradiation. We also confined irradiated areas on films in the range of microns to sub-micron to ascertain the lateral distribution of displaced oxygen, while establishing vertical Co/CoO interfaces which would lead to exchange bias across said interfaces. Irradiated films were characterized by SQUID magnetometry to estimate the effective O removal. Figure 1 (a) shows hysteresis loops for single layers irradiated with various doses and (b) multilayer systems irradiated with a fixed dose. In (a) we see that irradiating single layer films results in minimal O removal by measuring the saturation magnetization Ms. Geometrical confinement of the irradiated region indeed increases the Ms suggesting lateral O displacement, although this value is still only about 10% of bulk Co metal ((a) inset). The effect is much more pronounced in 0.8 nm CoO multilayers as indicated by the presence of perpendicular magnetic anisotropy (b). Figure 2 shows a loop shift for the multilayer (green) after field cooling demonstrating the formation of vertical Co/CoO interfaces post irradiation. This result is not seen in a single layer system (orange) as the layer is too thick to maintain a well-defined interface. These findings present new opportunities of device fabrication in single and bilayer systems.

Similar to electrical currents flowing through magnetic multilayers [1,2], thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin currents and generate ‘thermal’ spin-transfer torques large enough to induce magnetization dynamics on the free layer [3, 4]. The relation of spin current, charge current and heat current was theoretically described by Bauer et al. using Onsager’s reciprocity rule [5]. According to Onsager’s law, spin currents can be produced by bias voltages or thermal gradients and investigated in terms of spin-Seebeck effect in magnetic multilayers. First, Hatami et al. theoretically studied the spin-Seebeck effect in spin-valves and introduced the concept of thermal spin-transfer torques. They predicted that the thermally induced spin current creates an imbalance on the interface between non-magnetic and ferromagnetic layers due to collisions (electron-electron and electron-phonon interactions) [3]. Thermal spin-transfer torques were studied experimentally within asymmetric Co/Cu/Co nanowire spin-valves which exhibit switching field changes under varying a.c. currents causing Joule heating [6]. In magnetic tunnel junctions, it was theoretically predicted that temperature differences of around 10 K over an ultrathin barrier (1 nm) can create magnetization dynamics in Fe/MgO/Fe magnetic tunnel junctions [4]. The spin-Seebeck effect has been studied on CoFeB/MgO/CoFeB magnetic tunnel junctions using different heating methods such as Joule heating, heating with Peltier elements, as well as laser heating [8-14]. Recently, it was shown that using Co2FeAl as a reference layer improves tunneling magneto-Seebeck (TMS) in magnetic tunnel junctions [7]. Here, we describe a novel experimental approach and setup to observe effects of thermal gradients within magnetic tunnel junctions with Heusler compounds by using the microresonator ferromagnetic resonance (µR-FMR) method under laser heating. Initially, microresonators (sh

The fundamental oscillation mode of magnetic vortices in thin-film elements has been proposed as working principle for spin-torque-driven nano-oscillators [Nat. Phys., 3:498, 2007]. Commercial applications require tuning of the output frequency by external parameters, such as spin-polarized currents. The tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. The fundamental frequency is determined by the saturation magnetisation, Ms, as well as the geometrical confinement of the magnetisation i.e. the diameter and height of a magnetic disk. Our micromagnetic simulations have shown that if regions with different Ms can be induced in a magnetic disk, multiple precession frequencies can be generated. Here, we show that ion implantation [Phys. Rev. B 73, 184410, 2006] is a novel route to fabricate such devices. Permalloy (Py) disks of various diameters and thicknesses were patterned and contacted to study the interaction of an applied AC current with the magnetic vortex. Using a conventional lock-in technique, the resonance frequencies are measured based on the anisotropic magnetoresistance (AMR) effect. Regions of different Ms are induced in single disks by ion implantation, yielding different resonance frequencies corresponding to the specific area where the core is precessing. The work represents a novel way to obtain multiple oscillation frequencies from a single disk.

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation, i.e. the diameter and height of the magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. We show that ion implantation [5] is a novel route to fabricate such devices. Permalloy (Py) disks of various diameters and thicknesses were prepared using electron beam lithography followed by electron beam evaporation. Individual disks were contacted by gold leads to study the interaction of spin-polarized current with the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements. The magnetic field dependence of the vortex position can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters, whereas larger field sensitivity is present in larger disks (Figure 1 (b)). Magnetotransport measurements on electrically contacted disks show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 1 (c)). Using a conventional lock-in technique, the resonance frequencies are measured for disks with different radii as shown in Figure 2 (a), with the inset showing the scanning electron microscope image of an

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design [2, 3]. Using micromagnetic simulations, [4] we show that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Experimentally we employ ion implantation as a promising method to fabricate such devices [5]. Disks with different radii- 0.5 µm to 4 µm, thicknesses- 25 nm and 30 nm and lateral electrical contacts were prepared using electron beam lithography followed by electron beam evaporation to study the formation of magnetic vortices with respect to size and thickness. Magnetotransport measurements (Fig. 1(a)) show the presence of anisotropic magnetoresistance (AMR. The resonance frequencies measured using a lock-in technique on 25 nm thick permalloy disks are shown in Fig. 1(b). The disks were subsequently subjected to partial ion irradiation and the induced modification of the resonance frequency will be presented. The Nanofabrication Facilities Rossendorf at the IBC is gratefully acknowledged. Funding : Helmholtz Young Investigator Initiative Grant No. VH-N6-1048.

Spintronic devices are often patterned from continuous films into micro- or nanostructures. Fabrication of those nano-devices is self-limited and depends on the lateral resolution of the chosen fabrication method. Ion irradiation offers an alternative route to introduce smaller magnetic patterns limited by the size of the ion beam. Irradiation of oxide materials can cause chemical reduction and lead to the local formation of metallic species. By using the oxide family of ferromagnets (e.g., Fe, Ni and Co), reduction leads to the formation of ferromagnetic and conducting volumes limited by the size of the ion irradiated area that are embedded into a non-magnetic and insulating matrix. On the other hand, the physical mechanism behind ion irradiation-induced oxide reduction could not be explained. Therefore, our studies focus on ion (H, He, Ne, O) irradiated cobalt-oxide (CoO or Co3O4) systems in order to explain the physics behind the process. Also, the knowledge is being exploited to tune exchange-bias direction, prepare nano contacts for synchronized spin torque oscillators, and to form topographically stabilized magnetic skyrmions.

Magnetic tunnel junctions have been commonly used in spintronics applications, such as magnetic random access memory (M-RAM), spin transfer torque RAM (STT-RAM) and hard disc drive (HDD) because of high storage capacity. A spin polarized current flowing through a ferromagnetic layer can exert spin-transfer-torque (STT) on the local magnetization. When we apply thermal gradient across the junction we can induce what is called thermal spin transfer torque (T-STT). In this study, the microresonator FMR technique is used in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradients across the barrier. Details of resonator fabrication and preliminary measurements are presented. This work is supported by DFG-SPP1538.

The magnetic “vortex” is a potential candidate for future spintronic devices, like frequency sensors [S. Kasai, et al. PRL 97, 107204 (2006)] [R. Moriya, et al. Nat. Phys. 4:368 (2008)], spin torque oscillators [V. S. Pribiag, et al. Nat. Phys. 3:498 (2007)], and tunable magnonic crystals [J. Shibata, et al. PRB 67, 224404 (2003)]. The fundamental frequency is determined by the saturation magnetisation, as well as the geometrical confinement of the magnetisation i.e. the diameter and height of a magnetic disk. In this study, Permalloy disks (with diameters ranging from 1µm to 8µm) are patterned and contacted to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect, X-ray photoemission electron microscopy and magnetotransport measurements. The resonance frequency is measured using a lock-in technique based on the anisotropic magnetoresistance effect. Modification of the resonance frequency by ion irradiation will be presented.

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation e.g. the diameter and height of a magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Ion implantation is a promising method to fabricate such devices [5]. To study the formation of magnetic vortices with respect to size and thickness, disks with different radii- 0.5 µm to 4 µm and thicknesses- 25 nm and 30 nm were prepared using electron beam lithography followed by electron beam evaporation. Moreover, to allow for electrical measurements, the single disks were contacted by gold leads to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements. The magnetic field dependence can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters whereas larger field sensitivity is present in larger disks (Figure 1 (b)). Magnetotransport measurements on electrically contacted disks (Figure 2 (a)) show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 2 (b)). Additionally, to the shown static DC measurements, AC measurements are accessibl

MgO-based magnetic tunnel junctions are commonly used in spintronic device applications, such as recent spin transfer torque random access memory (STT-RAM) because of their non-volatility, fast switching and high storage capacity. Spin transfer torque is defined as a spin polarized current flowing through a ferromagnet exerting a torque on the local magnetization. With thermal spin transfer torque (T-STT), thermally excited electron transport is used instead of spin polarized charge current and provides an interesting way of using thermoelectric effects in magnetic storage applications. Our study focuses on fundamental experimental research aimed at demonstrating that thermal gradients can generate spin-transfer torques in MgO-based magnetic tunnel junctions (MTJs). We use microresonators in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradient across the barrier. This work is supported by DFG-SPP1538

The origin of the ferromagnetic order in TM:TiO2 (TM: transition metal) systems is studied by investigating the interplay between structural order, defects and incorporation of implanted TM ions within the host lattice. The defect properties of the host TiO2 films are altered by preparing different microstructures of TiO2 (e.g. amorphous, polycrystalline anatase and epitaxial anatase). The difference in microstructure is also found to influence the incorporation of the implanted ions into the host lattice. The crystallographic incorporation of the implanted TM atom is found only in crystalline films. Moreover, it is observed that the suppression of the dopant related secondary phases can also be achieved by changing the microstructure. Based on this discussion we propose an ideal microstructural candidate for a dilute magnetic oxide material based on our results.

The effect of H treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The treatment was realized by H+ irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm−2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration. Superparamagnetic B2-Fe60Al40 films were annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations may be mostly due to structural changes.

MgO-based magnetic tunnel junctions are commonly used in spintronic device applications, such as recent spin transfer torque random access memory (STT-RAM) because of their non-volatility, fast switching and high storage capacity. Spin transfer torque is defined as a spin polarized current flowing through a ferromagnet exerting a torque on the local magnetization. With thermal spin transfer torque (T-STT), thermally excited electron transport is used instead of spin polarized charge current and provides an interesting way of using thermoelectric effects in magnetic storage applications. Our study focuses on fundamental experimental research aimed at demonstrating that thermal gradients can generate spin-transfer torques in MgO-based magnetic tunnel junctions (MTJs). We use microresonators in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradient across the barrier. This work is supported by DFG-SPP1538

We report effect of the annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. The angular resolved ferromagnetic resonance measurements results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225 °C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliquity may be advantageous for specific applications such as spin-transfer oscillators.

The effect of H treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The treatment was realized by H+ irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm−2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration. Superparamagnetic B2-Fe60Al40 films were annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations may be mostly due to structural changes.

The influence of hydrogen on magnetic properties and defects of metallic thin films based on FeAl alloys was investigated. Therefore, hydrogen ions have been implanted with different fluences into disordered Fe60Al40 thin films. Magneto-optical Kerr effect showed an increase of coercivity with increasing ion fluence. The treatment of paramagnetic Fe60Al40 thin films in a climate chamber, on the other hand, led to an establishment of ferromagnetism. Elastic Recoil Detection Analysis showed no hydrogen in the implanted and climate chamber treated samples. However, positron annihilation measurements suggest storage of hydrogen in vacancies. The origin of ferromagnetism was investigated with further methods.

Due to chemochromism, Mg2Me (Me=Fe, Co, Ni) based alloys are low-cost and rare-earth-free candidates for switchable mirrors upon hydrogen loading. In order to understand the basic physical properties of Mg2Fe based thin films and its hydride, as-sputtered as well as hydrogen loaded films have been investigated using magnetometry, X-ray diffraction, 4-point probe sheet resistance technique and positron annihilation spectroscopy (PAS). The interplay of hydrogen loading, the magnetic moment, and structural properties like the sizes and chemical decoration of open volume defects in thin films detected by PAS will be presented.

Mg2Fe(x)Si(1-x) – hydride is a promising multifunctional material in terms of magnetic applications due to a dramatic change in their magnetic, optical and electronic properties upon hydrogen loading. Therefore they are capable of potential applications, e.g. hydrogen sensors for use as safety monitors wherever hydrogen is used, stored, or produced and storage devices. In order to understand the physical background of Mg2(FeSi) based systems as well as their hydrides, comprehensive investigations were performed on as-grown and hydrogen loaded 250 nm thick Mg2Fe(x)Si(1-x) (x= 0; 0.25; 0.50; 0.75; 0.90; 1.00) films using magnetometry, X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS). Magnetometry results revealed that upon hydrogen loading volume magnetic properties of the system transforms from superparamagnetic- and spin glass-like behavior to ferromagnetic behavior with high Curie temperature. Likewise, it is found that the hydrogen loading and Fe concentration have direct consequences on the structural properties, these can be explained either by an amorphisation process or by the formation of very small nanocrystalline particles probed by XRD measurements. Furthermore, different sizes and chemical decoration of open-volume defects has been observed by PAS. The knowledge gained from these studies can be use for monitoring those characteristics that change in the presence of hydrogen.

We report effect of the annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. The angular resolved ferromagnetic resonance measurements results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225 °C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliquity may be advantageous for specific applications such as spin-transfer oscillators.

Amorphous, polycrystalline anatase and epitaxial anatase TiO2 films have been implanted with 5 at. % Co+. The magnetic and structural properties of different microstructures of TiO2:Co, along with the local coordination of the implanted Co atoms within the host lattice are investigated. In amorphous TiO2:Co film, Co atoms are in the (II) oxidation state with a complex coordination and exhibit a paramagnetic response. However, for the TiO2:Co epitaxial and polycrystalline anatase films, Co atoms have a distorted octahedral (II) oxygen coordination assigned to a substitutional environment with traces of metallic Co clusters, which gives a rise to a superparamagnetic behavior. Despite the incorporation of the implanted atoms into the host lattice, high temperature ferromagnetism is absent in the films. On the other hand, it is found that the concentration and size of the implantation-induced nanoclusters and the magnetic properties of TiO2:Co films have a strong dependency on the initial microstructure of TiO2. Consequently, metallic nanocluster formation within ion implantation prepared transition metal doped TiO2 can be suppressed by tuning the film microstructure.

The structural, magnetic, and magnetocaloric properties of epitaxial Ni-Co-Mn-Al thin flms with different compositions have been studied. The fims were deposited on MgO(001) substrates by co-sputtering on heated substrates. All films show a martensitic transition where the transition temperatures are strongly dependent on the composition. The structure of the martensite phase was shown to be 14M. The metamagnetic martensitic transition occurs from a strong ferromagnetic austenite to a weak magnetic martensite. The structural properties of the films were investigated by atomic force microscopy and temperature dependent X-ray diraction. Magnetic and magnetocaloric properties were analyzed using temperature dependent and isothermal magnetization measurements. We found that Ni41Co10:4Mn34:8Al13:8 films show giant inverse magnetocaloric effects with magnetic entropy change of 5.8 J /kg K for deltaH = 1 T.

Ion irradiation induced modifications of the thermomagnetic properties of equiatomic FeRh thin films have been investigated. The application of 20 keV Ne+ ions at different fluencies leads to broadening of the antiferromagnetic to ferromagnetic phase transition as well as a shift towards lower temperatures with increasing ion fluence. Moreover, the ferromagnetic background at low temperatures generated by the ion irradiation leads to pronounced saturation magnetization at 5 K. Complete erasure of the transition, i.e. ferromagnetic ordering through the whole temperature regime was achieved at a Ne+ fluence of 3E14 cm-2. It does not coincide with the complete randomization of the chemical ordering of the crystal lattice.

We study effect of the initial structural order on the resulting magnetic properties of the manganese implanted TiO2 films. Different microstructures of as-grown TiO2 films, namely amorphous, polycrystalline anatase and epitaxial anatase, have been implant-doped with Mn+ up to a concentration of 5 at.%. We found that the different initial structures lead to different defect and charge carrier concentrations, and as a result, strongly influence the magnetic properties upon implantation. Depending on the initial microstructure, paramagnetism, secondary phases related magnetic properties as well as ferromagnetism could be observed in the films.