Gd-Co Films Research Articles

An investigation of the effect of chemical composition and temperature on the resistance and hardness of thin amorphous Gd-Fe and Gd-Co systems

The effect of chemical composition on the resistance, the resistivity, the temperature stability of resistance and the hardness of thin amorphous Gd-Fe and Gd-Co films was investigated. The maximum resistivity (3.2 x 10 -6 Ω m) for Gd-Fe films was observed at 35 wt.% Fe and for Gd-Co films (3.5 x 10 -6 Ω m) at about 25 wt.% Co. Gd-Fe films with an iron content below 56 wt.% had a negative temperature coefficient of resistance (TCR). Positive TCR values were obtained at higher iron contents. For Gd-Co films positive TCR values were obtained at cobalt contents exceeding 43 wt.%. At compositions of 19.6, 41.0 and 43.0 wt.% Co the resistance was not temperature dependent in the range 20–120 °C. The hardness of the films increased with increase in the transition metal content, with maximum values of 7.0 x 10 9 N m -2 for Gd-Fe films and of about 8.7 x 10 9 N m -2 for Gd-Co films.

Electron spectroscopy studies on amorphous GdFe and GdCo alloys

I n situ XPS photoelectron studies on amorphous thermally evaporated GdFe and GdCo films have been made under UHV conditions. The results were used to test the conventional concept of charge transfer, which had been applied to the materials under discussion. The XPS binding energies were found to be identical in the pure elements and the alloys, suggesting that the core levels in a-GdFe and a-GdCo are not very sensitive to a change in the chemical environment. Thus, it was concluded that the transfer of charge from Gd to the transition metal d bands, if existing at all, must be smaller than one electron per Gd atom. The preferential oxidation of Gd in GdFe and GdCo films was found to be characteristically reflected in the low-energy transitions of the Auger spectra, which hence were used to distinguish between the clean and the oxidized state of Gd. The influence of oxidation from the Gd 4d and 4f levels was characterized in some separate experiments on pure Gd.

The structure and magnetic anisotropy of amorphous Gd-Co films

The structure of amorphous Gd-Co alloy films has been investigated by electron diffraction. The films were prepared by bias sputtering on liquid nitrogen-cooled NaCl substrates. The films were in the 400- 800 A thickness range. Magnetic domains were observed by Lorentz microscopy. Hysteresis loops were measured by Faraday magneto-optic effect with the applied field perpendicular to the film surface. Elastically scattered electron intensity and reduced radial distribution functions are significantly different for the perpendicular anisotropic and in-plan anisotropic films. It can also be deduced from these experimental results that the perpendicular anisotropy is associated with a predominance of Gd-Co atom pairs.

Inhomogeneities and FMR spectra in some D.C. sputtered amorphous Gd-Co films

FMR technique has been shown to be capable of detecting chemical inhomogeneities present in some amorphous GdCo films. A group of bulk modes observed when the polarizing field is perpendicular to the film plane, have been shown to correspond to absorption from regions which differ slightly in their magnetization and hence in their relative Gd or Co concentration. Such inhomogeneities seem to increase with the bias voltage. A typical result shows that Gd concentration variation is in the range 1–2 at.% and which is beyond any chemical analysis used currently. These inhomogeneities increase with the bias voltage and are distributed, as it were, in the whole volume of the film in a random manner as shown by acid etching experiments. Vacuum annealing at T up to 290°C does not lead to any homogenization and argon anneal leads to a new situation with a very large in plane anisotropy besides a spin wave spectra now appears in all the samples.

Perpendicular magnetic anisotropy in sputtered GdCo films

Strong perpendicular magnetic anisotropy has been observed in GdCo films deposited by zero-bias sputtering with an Ar-N2 gas. As the nitrogen partial pressure of the sputtering gas increases, the perpendicular anisotropy constant increases and the Co sublattice moment of the films becomes large. The saturation magnetization of the films shows a steep temperature dependence near the magnetic compensation temperature. A molecular field theory indicates that the steep temperature dependence arises from the change in the exchange constant for the Gd-Co interaction. The perpendicular anisotropy may result from the exchange constant change.

Magnetic and structural properties of some amorphous rare earth-transition metal thin films

With a transmission electron microscope (TEM) we have studied various amorphous rare earth (RE) - transition metal (TM) and (Fe, Co)-B thin films. The greater part of the films has been produced by ultra high vacuum (UHV) vapour deposition. A series of amorphous Gd-Co films are made by sputter deposition as well. All films show an anisotropic microstructure. It consists of columnar regions surrounded by a network of less dense material. Using electron small angle scattering (SAS) and microfractography the columnar structure has been studied in more detail. This microstructure is caused by self shadowing of the obliquely incident vapour atoms. The column growth direction and the vapour flux orientation are correlated. So, the microstructure obtained will be influenced by the angle of vapour incidence. Vapour deposition from separate RE and TM sources produces in-plane anisotropy of the magnetization having its origin in the same mechanism that is responsible for the column formation. Our results indicate that perpendicular magnetic anisotropy may be related with 1) stress relief by oxygen take up during heating in the TEM, during vapour deposition in an oxygen contaminated vacuum, or during bias voltage sputtering and 2) composition fluctuations on the scale of the column size (50 - 250 Å) by RE-oxide formation at the low-density sites surrounding the rods.

Anisotropic Distribution of Atomic Pairs Induced by the Preferential Resputtering Effect in Amorphous Gd-Fe and Gd-Co Films

Mössbauer effect and X-ray diffraction of amorphous Gd-Fe films show that isolated Gd atoms are preferentially resputtered and a non-uniform distribution of Gd atoms is induced in amorphous Gd-T (T=3d transition metal) films prepared by a sputtering method with negative bias. The resputtering effect of isolated Gd atoms produces anisotropic distributions of T-T, Gd-T and Gd-Gd pairs in Gd-T films. The difference between the numbers of T-T pairs parallel and normal to the film amounts to 1020∼1021 pairs/cm3. This number of T-T pairs is appropriate to account for the oserved anisotropy of amorphus Gd-Co films. It is coucluded that the anisotropic distribution of atomic pairs is the most important origin of the magnetic uniaxial anisotropy induced by bias sputtering.

Influence of inert gas incorporation on uniaxial anisotropy of sputtered GdCo thin films

A study was made of the gas content and uniaxial anisotropy of GdCo films as a function of bias voltage and gas pressure. Unlike previous studies of GdCo, in this investigation, a multi-target sputtering system was used, making it possible to keep the Gd/Co ratio (and hence 4πM) relatively constant while the bias and pressure were varied. For low bias voltages, the anisotropy was found to increase with bias as has been reported in the literature. However, unlike previous studies, we found that the anisotropy reached a peak value at ∼200 V and then decreased with bias at higher voltages. When argon was used as the sputtering gas, it was found that the gas content in the film also peaked at ∼200 V; with neon, the gas content did not peak but decreased with bias at voltages over ∼100 V. Samples deposited with an argon pressure of 50 mTorr show an approximate proportionality between anisotropy and gas content, suggesting that the presence of the gas is at least partly responsible for the generation of growth-induced anisotropy in GdCo films.

Phase separation as source of perpendicular anisotropy in amorphous GdCo

The source of perpendicular anisotropy (PA) in 0.05 μ thick, evaporated amorphous GdCo films was investigated by correlating the magnetic domain structure, as observed in the Lorentz mode with film structure, as observed with high resolution electron microscopy and diffraction, as functions of post deposition in situ anneal and elevated substrate temperature. A strong void network was found to anneal out above 500 °K at an apparent glass transition. PA was developed either together with this or at slightly higher temperatures and could be correlated to the appearance of 60–100 Å wide columnar arrays of two separate amorphous phases. The phase separation is evident also in a splitting of the single broad diffraction peak, normally observed in homogeneous amorphous deposits without PA, into two distinct components. Deposition at substrate temperatures above this glass transition results in amorphous films which crystallize on annealing without development of PA. From this, PA is thought to arise from anisotropically shaped Co-rich regions in a transition stage between the homogeneous amorphous and crystalline states.

Effects of substrate bias and annealing on the properties of amorphous alloy films of Gd-Co, Gd-Fe, and Gd-Co-X (X=Mo,Cu,Au)

We have examined the dependence of various properties of sputter-deposited amorphous GdCo, GdFe, and GdCoX (X=Mo,Cu,Au) films upon substrate bias and annealing. Particular interest was directed to changes in magnetization, anisotropy, composition, x-ray diffraction patterns, and Ar content of the films. In the case of the binary films, we applied substrate bias voltages to 400 V. We found that for the GdCo system, Ku rises with increasingly negative bias voltage to about Vb=−200 V. Further increases in Vb cause Ku to decrease, so that Ku?0 for Vb?−400 V. Furthermore, it was found that the Ar content of the films tends to correlate with Vb, reaching a maximum for Vb?−200 V. X-ray diffraction patterns of these films also appear to correlate with Ku but in a more subtle manner than has been suggested by other workers. The results for amorphous GdFe films were considerably different. In particular, it was found that Ku was large for Vb?0 but decreased rapidly with negative bias. The behavior of ternary GdCoX films was similar to that of the binary GdCo films, except that the x-ray diffraction patterns showed little dependence on Vb. On being annealed for 4 h at 200 °C, the binary films show no change in magnetization, composition, or x-ray diffraction profile, but do experience a decrease in Ku by about a factor of 2. The situation is similar for the GdCoCu and GdCoAu films except that the temperature dependence of the magnetization also changes dramatically. In contrast to these results, amorphous GdCoMo films undergo little or no change on annealing. Our results suggest that the incorporation of Ar into the films is closely related to the mechanism responsible for Ku in these materials; however, there exist data which conflict with this interpretation, so that the origin of Ku remains in doubt. On the other hand, we have established the limits to the effects of Vb on the material’s properties, and we present a comprehensive collection of empirical facts which will prove useful for preparing this class of materials with desired properties.

Different origin of the perpendicular anisotropy in amorphous Gd-Fe from Gd-Co films

In order to contribute to the investigations of the mechanism of positive K u induced in the amorphous R-T films, a magnetic study was made on the amorphous Gd-Fe and Gd-Co films prepared under various conditions. It is found that the origin of K u in the Gd-Fe films is quite different from that in the Gd-Co ones. In the case of Gd-Co, the positive K u is known to be induced by a resputtering effect and its physical origin is thought as an atomic pair ordering. However, a different mechanism of stress induced anisotropy is taken as the responsible one for the positive K u in the Gd-Fe films.

Inverted and biased loops in amorphous Gd-Co films

Amorphous Gd-Co films sputtered at substrate biases ≤100V showed compensation temperature differences of about 100°C between the film-glass (FG) and film-air (FA) surfaces, as measured by Kerr rotation. The films exhibited normal as well as inverted Kerr and Hall loops, but throughout the temperature range between compensation temperatures either the FG or FA surface, but not both, showed inverted Kerr loops. Inversion temperatures were found at which the inverted loop property was transferred from one film surface to the other. Biased loops were obtained from inverted loops by reducing the field amplitude in one polarity. The bias field, H B , was identified as the effective field of exchange-coupled Gd-Rich and Co-rich layers. By the use of H B data the interlayer wall energy density was estimated to be 0.9 ±0.2 ergs cm-2.

Perpendicular magnetic anisotropy in evaporated amorphous GdCo films

Amorphous GdCo films with strong perpendicular magnetic anisotropy were vacuum deposited by thermal evaporation of the constituents in an oxygen atmosphere of at least 3×10−8 Torr. In this paper the fabrication technique and the magnetic properties of the resulting GdCo films will be reported.

Determination of the Magnetic Anisotropy in Amorphous Gd-Co Films by Torque Measurement

physica status solidi (a)Volume 40, Issue 2 p. K135-K138 Miscellaneous Determination of the Magnetic Anisotropy in Amorphous Gd-Co Films by Torque Measurement R. Perthel, R. Perthel Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorW. Keilig, W. Keilig Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorH. Kosicik, H. Kosicik Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorU. RÖPKE, U. RÖPKE Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorC.-G. D'AMBLY, C.-G. D'AMBLY Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this author R. Perthel, R. Perthel Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorW. Keilig, W. Keilig Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorH. Kosicik, H. Kosicik Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorU. RÖPKE, U. RÖPKE Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this authorC.-G. D'AMBLY, C.-G. D'AMBLY Zentralinstitut für Festkörperphysik und Werkstofforschung der Akademie der Wissenschaften der DDR, Institutsteil für magnetische Werkstoffe, JenaSearch for more papers by this author First published: 16 April 1977 https://doi.org/10.1002/pssa.2210400249Citations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume40, Issue216 April 1977Pages K135-K138 RelatedInformation

MAGNETIC PROPERTIES OF SPUTTERED Gd-Co ALLOY FILMS

摘要 用射频溅射的方法制备得的钆钴膜具有垂直于膜面的单轴各向异性.电子衍射结果表明薄膜是非晶态的.电子探针分析证明钆和钴的“ 混合” 是均匀的.用极向克尔效应观察了样品的磁畴，并测量了相应的磁滞回线; 发现在一定的工艺条件下, 制备得的样品, 在退磁状态呈现条状畴, 并在一合适的外磁场作用下能转变为磁泡. Abstract 作者及机构信息 王荫君；陈书潮；郑德娟；李德忠；郭慧群；孟庆安 1. 中国科学院物理研究所 Authors and contacts Wang Yin-Jun;Chen Shu-chao;Zheng De-juan;Li De-zhong; Guo Hui-qun;Meng Qing-an 参考文献 [1] 施引文献

Magnetization processes in amorphous Gd-Co films near the compensation point

Magnetization processes were investigated in bias-sputtered amorphous Gd-Co films with a compensation line using the polar Kerr effect. The results suggest that the compensation line is an energetically favourable place for the domain wall. Near the compensation line the domain wall movement shows asymmetry.

The observation of stripe domains in amorphous GdCo films prepared by evaporation

Stripe domains are supported in thin magnetic films which exhibit a sufficiently strong perpendicular magnetic anisotropy. Amorphous magnetic thin films of most rare-earth/transition-metal alloys prepared by sputtering or by evaporation commonly exhibit such a domain structure. Until now exceptions have been strong enough to give stripe domains. Some observations of such domains in amorphous GdCo films evaporated at oblique incidence are reported.

Magnetization and magnetic anisotropy in evaporated GdCo amorphous films

Saturation magnetizations and magnetic anisotropy constants were determined for a series of amorphous GdCo films prepared by thermal evaporation. The films covered the composition range from Gd0.05Co0.95 to Gd0.40Co0.60 and were studied by means of ferromagnetic resonance and a force balance magnetometer. The films, in contrast to those prepared by sputtering, had a hard perpendicular direction of magnetization when Co was less than 91 at.%, and easy and moderate directions within the plane of the film. The anisotropy constant can be expressed in terms of sublattice magnetizations by Ku=0.660MCo2 +2.218MCoMGd+0.097MGd2. The results are explained based on a pair-ordering mechanism. The composition and temperature dependence of saturation magnetization is essentially the same in evaporated and sputtered films.

Structure and Magnetic Anisotropy of Amorphous Gd-Co Films

It is found that the structure of amorphous Gd-Co films, as revealed by x-ray diffraction, is correlated with the magnitude of bias voltage present during the sputter deposition. Films sputter deposited with zero bias voltage typically show one broad peak in an x-ray diffraction spectrum, and films sputter deposited with −100 volts bias show two broad peaks with a shoulder between them. These structural differences appear to be related to the perpendicular magnetic anisotropy in these films.

Amorphous Gd-Fe alloy films prepared by RF cosputtering technique

Amorphous Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> (0 < x < 0.35) thin films were prepared by RF cosputtering using an iron target covered partially with small gadolinium pieces. The composition dependences of saturation magnetization, hysteresis curves, and domain structures were studied. Spark-like domains were observed when the magnetization was reversed from saturation. The uniaxial anisotropy was induced perpendicular to the film plane. The average value of the perpendicular uniaxial anisotropy constant Ku was about 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> erg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Ku, however, decreases as the saturation moment decreases in the vicinity of room temperature compensation. The stripe domain width was varied from 0.3 to 4 microns as the saturation moment decreased from 300 to 20 gauss. These magnetic properties of amorphous Gd-Fe sputtered films are similar to those of amorphous Gd-Co films.