Scripta Metallurgica et Materialia最新文献

{"title":"Soft magnetic nanocrystalline materials","authors":"Giselher Herzer","doi":"10.1016/0956-716X(95)00397-E","DOIUrl":"10.1016/0956-716X(95)00397-E","url":null,"abstract":"<div><p>The microstructure property relationship in soft magnetic nanocrystalline Fe-base materials is surveyed: The basic mechanism is that the magneto-crystalline anisotropy of the small, randomly oriented bcc-Fe grains is averaged out by exchange interaction. The resulting magnetic behaviour can be well described with the random anisotropy model. The latter has been extended to multiphase materials including the case that the grain size exceeds the exchange length and, is able now to describe the hardening mechanism in the overannealed nanocrystalline state due to the precipitation of borides. Further, the crucial role of the coupling mechanism between the grains is discussed. Thus, as a function of temperature, a single sample combines a variety of phenomena ranging from soft, over hard to finally superparamagnetic behaviour. Finally it is shown, how the structural phases present lead to low or vanishing magnetostriction; the random anisotropy effect guarantees an essentially isotropic behaviour comparable to the amorphous case. Together with the suppressed magneto-crystalline anisotropy, the low magnetostriction provides the basis for the superior soft magnetic properties observed in particular compositions.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1741-1756"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00397-E","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87533978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure and magnetic properties of magnesium ferrite fine powders","authors":"S.A. Oliver,&nbsp;R.J. Willey,&nbsp;H.H. Hamdeh,&nbsp;G. Oliveri,&nbsp;G. Busca","doi":"10.1016/0956-716X(95)00412-O","DOIUrl":"10.1016/0956-716X(95)00412-O","url":null,"abstract":"<div><p>Fine powders of magnesium ferrite, MgFe₂O₄, were produced through the sol-gel supercritical drying method, with two portions then being calcined at 773 K and 1073 K. The powder structural and magnetic properties were determined from transmission electron microscope micrographs, x-ray diffraction, Mössbauer effect spectroscopy and magnetometry measurements. The powder structure matched the MgFe₂O₄ spinel phase, with small amounts of α-Fe₂O₃ being observed in heated samples. As-produced powders were superparamagnetic at room temperature, with single magnetic domain particle behavior being observed at low temperatures, and for the 1073 K heated sample. The particle size distribution for the as-produced powder was evaluated separately from the micrographs, by fitting the magnetization data to a weighted Langevin function, and by fitting Mössbauer spectra taken at temperatures from 25 K to 298 K. Very similar particle size distributions were found from all three methods. The average particle diameter was 11 nm for the as-produced powder, and increased for heated samples. The saturation magnetization and magnetocrystalline anisotropy energy density values were both consistent with bulk values, in contrast to the large differences between particle and bulk values described for other fine particle systems.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1695-1701"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00412-O","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83246382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic and structural properties of high coercivity nanocrystalline CoSm films with in-plane anisotropy","authors":"D.J. Sellmyer,&nbsp;Z.S. Shan,&nbsp;Y. Liu,&nbsp;S.H. Liou,&nbsp;S.S. Malhotra,&nbsp;B.W. Robertson","doi":"10.1016/0956-716X(95)00430-4","DOIUrl":"10.1016/0956-716X(95)00430-4","url":null,"abstract":"<div><p>This paper presents results and an overview of magnetic and nanostructural properties of CoSm alloys which have high potential for future ultra high-density longitudinal magnetic recording. These sputtered films consist of about 5 nm crystallites embedded in an amorphous matrix, with the easy axes of the nanocrystallites in the film plane. The films have high coercivities, 3–4 kOe, and other highly favorable properties. Fundamental aspects of the relationship between nanostructure and magnetic properties are discussed.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1545-1552"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00430-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83378239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of Cr addition on the magnetic softness of nanocrystalline FeCuNbSiB alloys","authors":"J. González,&nbsp;N. Murillo,&nbsp;I. Mondragón,&nbsp;J.M. Blanco,&nbsp;J. Echeberría,&nbsp;E. González,&nbsp;J.M. González","doi":"10.1016/0956-716X(95)00408-N","DOIUrl":"10.1016/0956-716X(95)00408-N","url":null,"abstract":"<div><p>The compositional dependence of the effective anisotropy of as-quenched and thermally treated, Cr substituted FeCuNbSiB melt spun samples, is examined through the results corresponding to the measurement of the transverse biased initial susceptibility. The analysis of these experimental data allowed us to evidence the occurrence of magnetization ripple and to evaluate the evolution with the thermal treatments of the so-called dispersion field and of the dimensions of the coupled magnetization regions underlying the measured values of the effective anisotropy. It is concluded that magnetostatic interactions play (in addition to exchange interactions) a major role on the formation of these coupled regions.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1757-1764"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00408-N","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82750809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thin film structures for low field granular giant magnetoresistance","authors":"Kevin R. Coffey,&nbsp;Todd L. Hylton,&nbsp;Michael A. Parker,&nbsp;J.Kent Howard","doi":"10.1016/0956-716X(95)00390-H","DOIUrl":"10.1016/0956-716X(95)00390-H","url":null,"abstract":"<div><p>Giant magnetoresistance (GMR) is a relatively new field of study pursued by scientists and technologists alike. A potential application of GMR thin films is the replacement of NiFe alloy thin films (having anisotropic magnetoresistance) to obtain greater signal. Applications of this type require that the GMR be obtained at low fields, on the order of 10 Oe. In this paper three types of granular GMR thin film structures are described: co-deposited heterogeneous alloys, granular bi-layers, and discontinuous multilayers. Experimental examples of each type are presented, and the field dependence of GMR for each structure is discussed. Only discontinuous multilayer thin film structures have shown suitable GMR at low fields, and the properties and microstructure of these thin films will be described in greater detail.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1593-1602"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00390-H","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77638188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Permanent magnets — New microstructural aspects","authors":"Josef Fidler,&nbsp;Johannes Bernardi,&nbsp;Thomas Schrefl","doi":"10.1016/0956-716X(95)00392-9","DOIUrl":"10.1016/0956-716X(95)00392-9","url":null,"abstract":"<div><p>The influence of the microstructure on the hard magnetic properties of rare earth-iron based magnetic materials with outstanding coercivities and energy density products is surveyed. Nd₂Fe₁₄B based permanent magnets exhibit a complex multiphase microstructure. The grain size of the magnets strongly depends on the processing technique. If dopant and substituent elements are added to conventional magnets, the coercivity is mostly increased and the remanence slightly decreased. Substituent elements such as Dy or Co mainly change the magnetocrystalline anisotropy and Curie temperature of the hard magnetic Nd₂Fe₁₄B-phase. Our systematical TEM-study shows that the dopants, because of their different effect on the microstructure, can be divided into two groups independently of the processing technique, each with similar microstructural features. Secondary phases in the form of precipitates or new intergranular phases are formed after the dotation. Both types of dopants partly increase the coercivity or improve corrosion resistance. If a combination of type 1 and type 2 dopant elements to Nd-Fe-B or (Nd,Dy)-(Fe,Co)-B magnets is chosen, the coercivity and corrosion resistance is considerably improved. Magnets of the type Nd-Fe-B:(Ga,Nb), Nd-Fe-B:(Cu,Nb), Nd-(Fe,Co)-B:(Al,Mo) and (Nd,Dy)-(Fe,Co)-B:(Al,V) were systematically investigated and were found to behave according to the microstructural predictions. Secondary, soft magnetic phases, such as α-Fe, play an important role in the new, composite type hard magnetic materials. Our numerical, finite element comparison of the coercivity and remanence enhancement of nanocrystalline Nd₂Fe₁₄B and Sm₂Fe₁₇N_2.7 isotropic magnets show that the dipolar and exchange interactions between the hard and soft magnetic grains control the exchange hardening. The remanence and the coercivity of exchange hardened, nanocrystalline, hard magnets sensitively depend on microstructural features, such as the grain size and the volume fraction of the soft magnetic phase.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1781-1791"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00392-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80975746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Micromagnetic and microstructural studies of NdFeB by TEM","authors":"J.N. Chapman,&nbsp;L.J. Heyderman,&nbsp;S. Young,&nbsp;D.M. Donnet,&nbsp;P.Z. Zhang ,&nbsp;H.A. Davies","doi":"10.1016/0956-716X(95)00418-U","DOIUrl":"10.1016/0956-716X(95)00418-U","url":null,"abstract":"<div><p>Transmission electron microscopy has been used to study the magnetic and physical microstructure of thinned samples of NdFeB. Various compositions of sintered material and nanocrystalline melt-spun ribbon have been studied. The mean grain size in the materials ranges from 3 μm in the sintered material down to 20nm in the ribbon and this has a pronounced effect on the domain structures supported. Details of the magnetisation distribution both within grains and around boundaries are given and these are discussed in terms of the observed bulk magnetic properties.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1807-1816"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00418-U","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77266512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropy, exchange coupling and phase transition in bilayer systems","authors":"Xiao Hu,&nbsp;Yoshiyuki Kawazoe","doi":"10.1016/0956-716X(95)00429-Y","DOIUrl":"10.1016/0956-716X(95)00429-Y","url":null,"abstract":"<div><p>Phase transitions in magnetic multilayer structures are studied with mean-field theory. Transitions between different magnetization configurations in bilayer systems with different anisotropies are discussed by means of variational method. The responsible mechanism is the competition between the anisotropy energy and the exchange coupling. The para-ferro magnetic phase transition in a ferromagnetic bilayer system is investigated with the Ginzburg-Landau theory. The effect of finiteness of the layer thickness has been revealed. Critical phenomena according to the variance of the layer thickness are clarified.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1841-1847"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00429-Y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89044099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the nitrogen occupation in the Y2Fe17 lattice","authors":"Y.D. Zhang ,&nbsp;D.P. Yang ,&nbsp;J.I. Budnick ,&nbsp;W.A. Hines ,&nbsp;W.Q. Xu ,&nbsp;N.X. Shen ,&nbsp;D.M. Pease ,&nbsp;W.G. Fernando ,&nbsp;T.D. Xiao","doi":"10.1016/0956-716X(95)00406-L","DOIUrl":"10.1016/0956-716X(95)00406-L","url":null,"abstract":"","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1817-1824"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00406-L","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76063577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nanocrystallized thin films of transition metal obtained by low energy cluster beam deposition","authors":"V. Dupuis ,&nbsp;J.P. Perez ,&nbsp;J. Tuaillon ,&nbsp;V. Paillard ,&nbsp;P. Mélinon ,&nbsp;G. Guiraud ,&nbsp;J.P. Dupin ,&nbsp;A. Perez ,&nbsp;L. Thomas ,&nbsp;B. Barbara ,&nbsp;B. Bouchet","doi":"10.1016/0956-716X(95)00400-P","DOIUrl":"10.1016/0956-716X(95)00400-P","url":null,"abstract":"<div><p>Nanocrystallized thin films of iron obtained from low energy cluster beam deposition (LECBD) have been produced by adjusting different source parameters and elaboration conditions in an attempt to control the size distribution of supported clusters, In all cases, the films exhibit a nanostructure characteristic of the LECBD technique (mean 5 nm-diameter of the particles) and only the percentage of oxide in the form of a thin skin surrounding the particles changes. The specific magnetic behavior of these weakly correlated entities is described by ferromagnetic resonance and magnetization measurements. We showed that the magnetic properties of these cluster assembled materials can be interpreted using the random anisotropy model with a scale law related to grain size.</p><p>The increasing interest of the scientific community in the magnetism of “small particles”¹ is mainly driven by their potential application as high density storage devices^2,3. From the Stoner criterion, the size and the first-neighbor number reduction would be favourable to ferromagnetism in transition metals. In this context, metallic clusters are interesting for their large <span><math><mtext>surface</mtext><mtext>volume</mtext></math></span> ratio but they are very oxygen reactive. By varying the elaboration conditions (vacuum quality, substrate temperature, size distribution of the incident clusters…) we obtained nanostructured iron-films by Low Energy Cluster Beam Deposition (LECBD). This paper is mainly concerned with the structural and magnetic properties of these original cluster assembled materials.</p><p>The laser vaporization source operating in the laboratory of Lyon⁴ allows the production of an intense cluster beam in a wide range of size (from few to a thousand atoms per cluster), to synthetize thin films of any kind of materials even the most refractory. Roughly, the plasma created at the laser impact on the iron rod, is thermalized by a synchronized high pressure (5 bars) helium pulse. The nascent clusters are then rapidly quenched during the following isentropic expansion into the vacuum (10⁻⁴ torr) chamber containing the source. The size distributions of clusters are checked by time-of-flight mass spectrometry before deposition. The deposit of neutral clusters at low energy on various substrates are subsequently realized after the retraction of the time-of-flight acceleration grids. This type of source produces cold clusters and we succeeded previously in the stabilisation of very low size fullerenes⁴. In particular we deposited C₂₀-clusters without fragmentation on the substrate in order to produce original diamondlike structures⁴.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1563-1568"},"PeriodicalIF":0.0,"publicationDate":"1995-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0956-716X(95)00400-P","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74070190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}