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We report the crystallization study of CoFeB/MgO/CoFeB magnetic tunnel junctions using in-situ, time-resolved synchrotron-based x-ray diffraction and transmission electron microscopy. It was found that the crystallization of amorphous CoFeB electrodes occurs on a time scale of seconds during the postgrowth high temperature annealing. The crystallization can be well fit by the Johnson–Mehl–Avrami model and the effective activation energy of the process was determined to be 150 kJ/mol. The solid-state epitaxy mode of CoFeB was found to involve separate crystallization at different locations followed by subsequent merging of small grains, instead of layer-by-layer growth of CoFeB film along the MgO template.

A comprehensive study of the defects and impurity (Co)-driven ferromagnetism is undertaken in the oxide semiconductors: TiO(2), ZnO and CeO(2). The effect of magnetic (Co(2+)) and non-magnetic (Cu(2+)) impurities in conjunction with defects, such as oxygen vacancies (V(o)), have been thoroughly investigated. Analyses of the x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) data reveal the incorporation of cobalt in the lattice, with no signature of cobalt segregation. It is shown that oxygen vacancies are necessary for the ferromagnetic coupling in the Co-doped oxides mentioned above. The possible exchange mechanisms responsible for the ferromagnetism are discussed in light of the energy levels of dopants in the host oxides. In addition, Co and Cu co-doped TiO(2) samples are studied in order to understand the role of point defects in establishing room temperature ferromagnetism. The parameters calculated from the bound magnetic polaron (BMP) and Jorgensen's optical electronegativity models offer a satisfactory explanation of the defect-driven ferromagnetism in the doped/co-doped samples.

The ac susceptibility, electrical properties, and magnetotransport properties of the as-prepared MnxCu1−xO thin films (x=7%–29%) were studied in the temperature range of 2–300 K. The susceptibility measurement shows that ferromagnetic transition takes place for the samples with x≥14% below 100 K. The transport properties show the transition from variable-range-hopping to metalliclike behavior at the same transition temperature as the paramagnetism to ferromagnetism transition. The metal-insulator transition is a characteristic feature of magnetic ordering in this material.

In this paper, the magnetic properties of these films which deposited and annealed at different atmospheres were investigated. The experimental results show that the magnetic properties of yttrium iron garnet films prepared by rf magnetron sputtering method can be tuned with oxygen partial pressure in sputtering and annealing processes. The optimal condition is depositing in atmosphere of R=0 and annealing at 0.5Pa O2, or depositing in atmosphere of R=2% and annealed in vacuum.

In this study, the effective spin-mixing conductance in Ni80Fe20/Pt was investigated by measuring the interface-induced enhancement of the Gilbert damping constant. Ferromagnetic resonance spectra were measured in coplanar waveguide geometry with different incident microwave powers. The nonlinear behavior of normal Gilbert damping G0 and effective spin-mixing conductance g↑↓ have been observed when the incident microwave power is above a critical ac field hrf of 1.6 Oe. Both phenomena are explained by considering the coupling between spin coherent precession and spin wave modes. This work demonstrates the nonlinear behavior of the effective spin-mixing conductance g↑↓. It suggests that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect and should be avoided in future spin battery designs. The capability of tuning G0 and g↑↓ through the microwave power is also useful for the fundamental study on the damping mechanism.

A comparative study on the room temperature ferromagnetism of Co doped ZnO and CeO2 bulk samples is presented. Co–ZnO system has been observed to switch between ferromagnetic and paramagnetic by controlling the donor defects, interstitial zinc: Zni. On the other hand, Co–CeO2 is always ferromagnetic. However, ferromagnetism increases/decreases with increase/decrease in donor defects, oxygen vacancies: VO. Systemic structural, magnetic, and transport analyses reveal that the nature of donor defects and host oxide plays a vital role in establishing ferromagnetism. This study provides an insight into the underlying mechanisms that are responsible for the ferromagnetism in Co–ZnO and Co–CeO2. Moreover, the proposed mechanisms are supported by the electronic structure of magnetic impurity ions and defects.

Magnetic materials with tunable ferromagnetic resonant (FMR) frequencies are highly desirable in microwave devices. In this manuscript, we demonstrate that the natural FMR of Ni90Fe10 nanowire array can be tuned continuously from 8.2 to 11.7 GHz by choosing different remanent states. Theoretical model based on magnetostatic interaction among nanowires has been developed to explain the observed phenomena.

The electronic structure and magnetic properties of Co-doped CeO(2) are theoretically investigated by first principles calculations based on the density functional theory + U (DFT+U) methods, using the WIEN2k package. With the presence of oxygen vacancies (V(O)) in CeO(2), d and f orbits of Ce are obviously pulled closer to the Fermi level, but without spin polarization. On the other hand, in Co-doped CeO(2), V(O) defects can lead to strong ferromagnetic coupling between the nearest neighboring Co ions. Such ferromagnetic exchange coupling is mainly attributed to spin splitting of Co 3d states, via electrons trapped in V(O). The results provide direct evidence for the F-center mediated exchange interaction in oxide-based magnetic semiconductors.

V-doped anatase TiO2 films were fabricated by a non-vacuum liquid phase deposition (LPD) technique on glass substrates. All as-prepared films are amorphous, which are highly crystallized to be anatase TiO2 after air or vacuum annealing at 600 °C. A nanocrystal structure with a grain size of about 10 nm was confirmed by XRD and high resolution transmission electron microscopy (HRTEM). It is found that in the LPD process, the in situ substitution of Ti by V ions occurred, and V atoms were distributed very uniformly in the TiO2 matrix. The air-annealed V0.025Ti0.975O2 samples are paramagnetic, while the vacuum annealed samples clearly exhibit room-temperature ferromagnetism (FM) with a magnetic moment of 1.1 μB/V. Our results unambiguously show that oxygen vacancies play a critical role in generating FM in doped TiO2 and an F-centre mechanism for diluted FM is confirmed.

Yttrium iron garnet films were grown by radio frequency magnetron sputtering on Si(111) substrate with and without CeO2 buffer layer, and influence of CeO2 buffer on the microstructure and magnetic behaviors of the films were investigated. As compared with the film without buffer, a larger saturation magnetizaton (Ms), lower coercive force (Hc), and higher remnant magnetization (Mr) were obtained due to the introduction of CeO2 layer. The higher Ms results from the denser structure and the smaller content of Fe2+ ions. The lower Hc and higher Mr can be explained by the small surface roughness and crystal grains size. The film on CeO2 buffer layer possess fine microstructure and its surface roughness is smaller than the unbuffered films, which provides an increased exchange between the crystal grains and an enhanced spontaneous magnetization effect, leading to the higher remnant magnetization.

The effects of the copper-site holes and oxygen-site holes on structure, superconductivity, and normal state in ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ have been studied by use of a method in which the hole concentrations at both sites are varied independently. The filling of the ${\mathrm{Cu}}^{2+}$ holes and the ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ holes induces a tetragonal-to-orthorhombic structural transition. Such a behavior strongly supports the interpretation that the driving force for the bending of Cu-O-Cu bonds is the stabilization of the ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ antibonding interaction. The two hole-filling processes generate profoundly different effects on ${\mathit{T}}_{\mathit{c}}$ normal-state transport, and magnetic susceptibility. We will discuss the causes of these highly asymmetrical effects.

Mn (6.6–29.8%)-doped CuO thin film fabricated on a thermally oxidized silicon substrate by radio-frequency magnetron sputtering has been reported. The films were structurally characterized using x-ray diffraction with Rietveld refinement. The analysis indicates that Mn uniformly substituted at the Cu position in the CuO lattice. 5% cation vacancies were detected at the Cu sites and are supposed to be responsible for the p-type electrical conduction of Cu1−xMnxO films. No evidence for large scale Mn aggregation was found in the composition range analyzed. The origin of ferromagnetism was analyzed in the context of competition among several interactions among Mn and Cu ions. A chain model was developed to simulate the ferromagnetic behavior with the random Mn distribution in the samples. The consistency between simulation and experiment strongly indicates that the ferromagnetism mainly arises from the super-exchange interactions of Mn–O–Cu–O–Mn coupling in the [] chain and Mn–O–Mn coupling contributes to the antiferromagnetism.

Thin films of room temperature diluted magnetic oxides (DMO) of Co doped CeO2 (Ce0.97Co0.03O2−δ) with a predominant orientation of (001) have been deposited on Al2O3(0001) substrates. An Ar+ sputtering process has been applied to the as deposited films to investigate its effect on the films' ferromagnetic properties. With the aid of magnetic measurements, we find that Ar+ bombardment has an obvious effect on the magnetic properties of the as deposited films, i.e., the saturated magnetization moments (MS) are enhanced by Ar+ bombardment. More detailed work has been done to further explore the inherent mechanism. Ar+ sputtering was found to introduce additional oxygen vacancies (VO) into the as deposited films (through x-ray photoelectron spectroscopy and Raman spectral analysis), which should make a certain contribution to the enhanced MS observed for Ar+ sputtered films. The experimental results provide direct evidence of VO enhanced ferromagnetism of insulating DMO, and are consistent with the recently proposed F-center exchange coupling mechanism.

We report the study of the real-time evolution of tunneling magnetoresistance (TMR) in CoFeB∕MgO∕CoFeB junctions during annealing at 380°C. The TMR quickly developed at the early stage of the annealing, with 200% magnetoresistance observed in less than 10min, followed by a slow approach to saturation. This evolution of TMR was correlated with the structural changes, including crystallization of amorphous CoFeB electrodes and improvement of barrier quality during the annealing.

Single-phase La2(1−x)Co2xO3−δ polycrystalline samples with x=0%–8% were synthesized by the conventional ceramic method, and the effect of Co content on the magnetic behaviors has been systemically investigated. X-ray diffraction and x-ray photoelectron spectroscopy studies indicate no Co metal clusters or secondary magnetic phases in any samples in this study. It is found that the undoped or slightly doped samples show no ferromagnetic signal, while samples with x in the range of 0.5%–2% exhibit an exponential increase of saturation magnetization (Ms) as a function of Co concentration. When x increases beyond 2%, an inverse correlation between the magnetization and Co content was observed. We reported an Ms as large as 0.05emu∕g and a Curie temperature above RT in our samples, rendering Co:La2O3 a candidate diluted magnetic oxide for RT applications. Our results also strongly support the oxygen vacancy (F-center) mediated mechanism for RT ferromagnetism in transition-metal doped high-k oxides

Microwave assisted magnetization switching was investigated using Fe30Co70∕Al2O3∕Ni80Fe20 magnetic tunnel junctions incorporated with a coplanar waveguide. Coercivity reduction (or switching field) of Ni80Fe20 layer was reduced with a microwave excitation. It was found that the coercivity reduction depends on both frequency and power of the microwave. The numerical simulation based on the Landau-Lifshitz-Gilbert equation reproduced the trend of the experimental data. The results indicate that microwave can be an efficient mean to switch the magnetization of a thin film.

We report the fabrication of (Zn,Cr)Te films at room temperature by magnetron sputtering. Various structural and elemental characterizations revealed there was only a zinc blende phase from the ZnTe host and Cr atoms were distributed uniformly in these films. The magnetization measurement by superconducting quantum interference device magnetometer clearly showed that the samples were ferromagnetic at low temperatures with Curie temperature around 150K. The magnetic circular dichroism measurements confirmed that the observed ferromagnetism was originated from the interaction of substitutional Cr ions and ZnTe host. Transport measurement revealed typical semiconductor behaviors with the large negative magnetoresistance observed.

Rapid development and application of nanomaterials and nanotechnology make assessment of their potential health and environmental impacts on humans, non-human biota, and ecosystems imperative. Here we show that pumpkin plants (Cucurbita maxima), grown in an aqueous medium containing magnetite (Fe3O4) nanoparticles, can absorb, translocate, and accumulate the particles in the plant tissues. These results suggest that plants, as an important component of the environmental and ecological systems, need to be included when evaluating the overall fate, transport and exposure pathways of nanoparticles in the environment.

Highly oriented magnetite (Fe3O4) thin films have been produced by reactive sputtering in a mixture of hydrogen and argon. While different phases can be achieved by varying the ratio between hydrogen and argon, single phase magnetite films can be achieved with hydrogen concentration γ=0.75%–1%. For the sample grown at γ=1.0%, a Verwey transition at about 111K can be seen from the temperature dependence of the resistivity, which is confirmed in the magnetization measurements. Maximum magnetoresistance (MR) of about 13.8% is observed just about the Verwey transition at T=115K. MR results also suggest strong coupling among Fe3O4 nanoparticles originated from the Ruderman-Kittel-Kasuya-Yosida exchange interaction and dipolar interaction, which requires high order terms of (M∕Ms)2 to explain the MR behaviors. However, with the fields applied perpendicular to the plane, MR exhibits a distinct behavior. The MR values under the condition of low fields seem to show a linear relationship with ∣M∕MS∣.

Ce1−xCoxO2−δ films with the stoichiometry of x=0,0.03,0.06,0.1,0.125 were fabricated on Si(111) substrates using O2 assisted pulse laser deposition method. While pure CeO2 film is weak paramagnetism, integration of low Co content of 3at.% introduces ferromagnetim with a giant saturation moment (Ms) of 5μB∕Co at room temperature. Based on the first principle calculation, we attribute the giant magnetic moments to the combined contributions of spin polarized Co, Ce, and O atom with the enhancement of O vacancies. Higher Co content will depress the ferromagnetism, i.e., inverse correlation between Ms and Co contents, which is qualitatively validated by the calculated magnetic moments of Ce1−xCoxO2−δ with different Co content.

Highly (111) oriented Mn(6.6%–29.8%) doped CuO thin films have been fabricated on thermally oxidized silicon substrate by radio-frequency magnetron sputtering. X-ray photoelectronic spectroscopy and resistivity studies indicate that both Cu and Mn ions have 2+ valences in the film. Ferromagnetism has been observed for 15.2%–29.8% Mn doped CuO thin film with a transition temperature between 87.0 and 99.5K. The origin of ferromagnetism is analyzed in the context of competition among several interactions between Mn and Cu ions. Highly resistive nature of the films eliminates the carrier mediate mechanisms. The ferromagnetism arises from the ferromagnetic coupling between Mn ions mediated by Cu ions.

Microwave-assisted magnetization switching was investigated using Fe30Co70∕AlOx∕Ni80Fe20 magnetic tunnel junctions incorporated with a coplanar waveguide. Coercivity field of Ni80Fe20 layer was dramatically reduced in a small amplitude microwave. The authors eliminated the thermal effect in coercivity reduction by comparing two types of measurements which are with and without spin precession in the presence of microwave. It was found that the coercivity reduction depends on both frequency and power of the microwave. The numerical simulation based on Landau-Lifshitz-Gilbert equation reproduced the trend of the experimental data. The results indicate that microwave can be an efficient means to switch the magnetization of a thin film.

We have studied the index of refraction of periodic layered semiconductor–ferrite composite. Both the transmission matrix analysis and full-wave simulations confirm the existence of a negative index of refraction in the composite. We find that the magnitude of the negative index of refraction and its frequency range depend on the ratio of the semiconductor and ferrite layer thicknesses and the doping content of the semiconductor. At the long-wave approximation, we have obtained the explicit expression of the effective index of refraction, effective permittivity and effective permeability. The result shows that it is possible to fabricate a uniform negative index material with the layered composite.

We have prepared Co-doped ZnO bulks with a two-step method. The bulk samples are sintered at the temperature above 1000°C to get pure single phase and then treated by Zn vapor in a vacuum. Based on such two-step preparation, clear carrier induced ferromagnetism is found in Zn treated Co-doped ZnO bulks, which suggests that the magnetism mechanism can be of codoping effect. The onset of ferromagnetism is associated with the further increase of the hybridization of the impurity band with 3d states near the Fermi level when additional carrier induced to let the Stoner criterion for ferromagnetism to be satisfied.

Magnetic tunneling junctions (MTJs) with MgO tunnel barrier have been fabricated on both oriented and nonoriented buffer layers on Si(001) substrate by magnetron sputtering. FeCo∕MgO∕FeCo MTJs fabricated on oriented buffer layers show larger tunneling magnetoresistance (TMR) value up to 84% without high temperature postannealing, whereas those MTJs on nonoriented buffer layers show 45% of TMR. The high-resolution transmission electron microscopy images reveal an excellent morphology and very coherent crystal structure with FeCo(001)[110]∕MgO(001)[100]∕FeCo(001)[110] orientation. The results indicate that high TMR can be achieved without high temperature postannealing by sputtering deposition on appropriate oriented buffer layers.

A pseudo spin-valve (PSV) using amorphous CoNbZr alloy as a soft magnetic layer and buffer layer was proposed. The giant magnetoresistance (GMR), thermal annealing effect, and the performance were investigated. Antiparallel magnetization alignments were observed in the samples with 2–4nm CoNbZr layer and a maximum GMR of 6.5% was obtained. Furthermore, sandwich with relatively thick CoNbZr layer has a superior thermal stability to 400°C and a GMR enhancement to about 9%. After patterning to 6μm×1μm elliptic stripe, a single domain forms and the dynamic MR behavior indicates the stripe has a linear and stable GMR response. Therefore, it is believed that the PSVs with amorphous CoNbZr layers have good potentials for spin-electronic devices.

We have successfully fabricated composites consisting of aligned Fe flakes embedded in a polymer matrix. Similarly high values of permeability and permittivity have been achieved, resulting in potentially significant improvements in device miniaturization, impedance matching, and bandwidth. Various effective medium theory models fail to give accurate values of permeability and permittivity of flake/polymer composites, indicating that modifications are needed for flake shape inclusions.

Vanadium-doped ZnTe has been predicted to be one of the candidates for ferromagnetic semiconductors with a high Curie temperature [K. Sato and H. Katayama-Yoshida, Semicond. Sci. Technol. 17, 367 (2002)]. In this paper, we report the structural, magnetic, and transport properties of (Zn,V)Te films prepared by magnetron sputtering. Samples were fabricated on both GaAs and thermally oxidized silicon substrate at elevated temperature. Oriented sample (100) can be achieved on GaAs substrates and only polycrystalline samples are observed on Si substrates. X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) show no magnetic precipitates in the (Zn,V)Te film. The magnetization measurement shows that the oriented sample is paramagnetic at 5 K, while films on Si substrate shows weak ferromagnetism at 5 K. The sign of magnetoresistance (MR=[R(H)-R(0)]∕R(0)) gradually changes from negative to positive with temperature, and positive MR at high temperatures shows H2 dependence, indicating ordinary MR ...

We have fabricated CoNiFeGa single crystals with excellent superelasticity. The superelastic strains of 4% and 6.7% in compression have been obtained along the [001] and [110] directions, respectively. These single crystals show strong anisotropy in strains, superelastic parameters, and even transformation path related to the different crystalline directions. A large superelastic strain up to 11% has been obtained in tension test. The perfect superelasticities have also displayed in bending and torsion tests.

Cu2O has excellent optical properties and could be a good host semiconductor for dilute magnetic semiconductors because doped Cu2O is a p type and direct wide-band-gap semiconductor. In this work, Mn-doped Cu2O thin films were deposited on thermally oxidized silicon substrates by radio-frequency magnetron sputtering. X-ray diffraction results show that highly (200) oriented (Mn0.06Cu0.94)2O films can be achieved at elevated substrate temperature. X-ray photoelectronic spectroscopy confirms that the valence of copper in the films is only +1, and no other valence states. The Mn-doped Cu2O films show primary paramagnetic behaviors above 25K. Very weak ferromagnetic property interspersed with paramagnetic phase appears near 5K. The high magnetic moment of 5.3μB per Mn ion and high resistivity suggest the valence state of manganese is mainly +1.

Manganese is a common dopant to achieve dilute magnetic semiconductors. Most magnetic semiconductors are hole-type and the Curie temperature is critically depending on the holes concentration. Boron can be used to increase the holes concentration and enhance the Curie temperature. In systems with both Mn and B dopants, one must consider the magnetic properties of MnB. In this study, single phase MnB alloy has been fabricated and characterized. Magnetic properties have been studied using superconducting quantum interference device and vibrating sample magnetometer over a broad temperature range. Very high magnetization of about 113emu∕g at room temperature has been observed, which is much higher than previous reports. The Curie temperature is around 306 °C, similar to previously reported value.

Quaternary Heusler alloy Ni50Mn8Fe17Ga25 ribbons have been prepared by the melt-spun method. The ribbons exhibit large negative magnetoresistance (MR){=[R(H)−R(0)]∕R(0)} over a wide temperature region, particularly in the region during the martensitic phase transformation. The MR decreases significantly after annealing. The large MR is isotropic and is mainly attributed to the local magnetic disorders, magnetic clusters, and heterogeneity. The maximum MR at martensitic transformation may be due to the redistribution of electrons and the increase of phase boundary scattering. This feature adds a useful functionality to the already interesting Heusler alloys.

By oxidizing wedge-shaped Al films we were able to simultaneously fabricate Ni80Fe20/AlOx/Ni80Fe20 tunnel junctions with over, completely, and underoxidized barriers. We have systematically investigated TMR ratio, resistance, barrier height and thickness, and bias dependence along the wedge. The bias dependence of MR ratio is asymmetric in overoxidized regions and symmetric in underoxidized regions. The interesting bias dependences of resistance at parallel and antiparallel configurations will also be presented.

The exchange bias (EB) effect and magnetic domain structures of FeMnC/FeMn bilayers prepared by a facing target sputtering system were studied. Unusual doubly shifted hysteresis loops were observed in a series of FeMnC/FeMn bilayers when different magnetic fields were applied to induce the exchange bias. The temperature dependences of the double shifted loops were measured and the ferromagnetic resonance measurement reveals the existence of EB. The correlation between the microscopic domain structures and the magnetization reversal processes was discussed, which suggests that the domain structure distribution of the antiferromagnetic layer is responsible for the loop shift.

dc, ac field cool, and their various combinations were applied to standard top and bottom spin valves. While dc field cool from the above blocking temperatures helps to align the antiferromagnetic (AFM) spins, therefore introducing exchange bias, ac field cool statistically randomizes the AFM spins, thus effectively erasing it. The various combinations of these two processes help to separate the contribution to the total exchange bias from different AFM grain sizes. It is found that, compared to the smaller grains, the local exchange bias for larger AFM grains is smaller, but with better temperature stability. More detailed analysis of the temperature dependence of the exchange bias reveals that it is influenced not only by the exchange coupling between FM and AFM layers, but also the interaction among different AFM grains. Such interactions include the direct antiferromagnetic interactions among AFM grains, and the indirect ferromagnetic interaction through the adjacent FM layer. The net interaction is t...

The most dramatic changes in the properties of granular metals occur near the percolation threshold xc, which generally occurs at a volume fraction of approximately 0.50. There has been much speculation concerning the evolution of magnetic domains at xc, however, no direct observations have been produced. Using scanning electron microscopy with polarization analysis, we investigate the formation of domains in a series of granular Co‐Ag samples. We find xc to lie in the range [0.50, 0.55], and we report on the size and morphology of the observed domains. Below xc, a domain pattern appears which may be due either to interparticle correlations or to residual Co in the silver matrix; we have previously discussed the ramifications of this observation on an understanding of GMR. In this paper, we place limits on the latter of these two models. Above xc, the domains resemble ‘‘stripe domains’’ which have been observed in amorphous materials. This observation suggests the presence of anisotropy perpendicular to t...

Granular Co‐Ag materials with low Co contents exhibit giant magnetoresistance and single‐domain magnetic properties. In this paper, we discuss unusual hysteresis behavior that we have observed in Co‐rich samples, where the magnetization is approximately linear with the applied field up to saturation, and the coercivity and remnant magnetization are both nearly zero. We attribute this unusual behavior to a perpendicular anisotropy that depends on the nanostructure in the phase‐segregated materials. These results are corroborated by magnetic domain imaging using scanning electron microscopy with polarization analysis.

Thin films of iron nitrides have attracted much attention due to their superior magnetic properties. Conventional rf reactive sputtering using N2 gas encounters a number of difficulties, including mixed phases, which are alleviated by the use of NH3 gas. By controlling the partial pressure of NH3, we have been able to fabricate all stable Fe nitrides of ζ‐Fe2N, e‐Fe2–3N, and γ’‐Fe4N in single‐phase films. The structure has been determined using an x‐ray diffractometer. The magnetic properties have been investigated using VSM, SQUID magnetometers, and Mossbauer spectroscopy. All nitrides except Fe2N have high saturation moments with a large in‐plane anisotropy. The saturation moment decreases with increasing nitrogen concentration. The Mossbauer results, in excellent agreement with those from bulk samples, are consistent with structural results and magnetization measurements.

“H.-J. Fockel, Phys. Status Solidi B 139, 59 (1987). 9479 (1989). “J. B. Adams, W. F. Wolfer, and S. M. Foiles, Phys. Rev. B 40, “A. Berman and H. J. Juretschke, Phys. Rev. B 11, 2893 (1975). 7375 J. Appl. Phys. 69 (lo), 15 May 1991 0021-8979/91/107375-01$03.00 @ 1991 American Institute of Physics 7375