Scripta Metallurgica et Materialia最新文献

{"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}

{"title":"Thermally activated demagnetization in Fe-SiO2 granular solids","authors":"C. de Julián ,&nbsp;Anit K. Giri ,&nbsp;M.P. Morales ,&nbsp;J.M. González","doi":"10.1016/0956-716X(95)00416-S","DOIUrl":"10.1016/0956-716X(95)00416-S","url":null,"abstract":"<div><p>(SiO₂)_{1 − x}Fe_x samples, with 0.2 ≤ x ≤ 0.4, were prepared by high energy ball milling. We studied in these samples the temperature dependence of the magnetization, coercive force and thermally activated demagnetization parameters. From all these results it was concluded the occurrence, in all the examined samples, of two different maxima in the blocking temperature distributions, identified as corresponding to the extremes of the particle size distribution.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1709-1716"},"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)00416-S","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85053841","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":"Microstructure and giant magnetoresistance in granular and multilayer magnetic thin films","authors":"N. Thangaraj,&nbsp;Kannan M. Krishnan,&nbsp;R.F.C. Farrow","doi":"10.1016/0956-716X(95)00407-M","DOIUrl":"10.1016/0956-716X(95)00407-M","url":null,"abstract":"<div><p>The microstructure and magnetic properties of phase-separated (FeAg, CoAg) granular and multilayer Permalloy (Py)/Au magnetic thin films exhibiting giant magnetoresistance (GMR) havebeen investigated. Surprisingly, two Fe-Ag films of similar composition grown under identicalconditions and having substantially different microstructures yet display similar GMR. The microstructure of these films is characterized by Fe-rich or Co-rich regions respectively, 350–700 nm in extent and surrounded by a Ag-rich matrix. Within the Ag-rich regions, the Fe concentration varies from 20 to 25 atomic % and the Co concentration is ~16 at%. Within these regions essentially pure fcc Co particles and bcc Fe particles are in parallel and rotated epitaxial alignment respectively with the fcc Ag matrix. The Co and Fe particles are ~15 to 25Å in diameter. It is these small particles which account for the GMR exhibited by these alloys. This suggests that a size distribution of magnetic particles, sharply peaked at the optimum size with limited bulk segregation might give rise to larger GMR values. On the other hand, high resolution electron microscopy (HREM) analysis of as-grown permalloy (Py)/Au multilayers in (111) orientation revealed that the Au and Py layers have sharp interfaces with defects such as twin boundaries and misfit dislocations. The density of twin boundaries decreases from the Pt-seed layer to the top surface of the multilayer. An average of 1 twin boundary/195 nm² has been observed. On mild annealing, the twin density decreases and the multilayer interfaces become rough. The magnetoresistance of the as-grown Py/Au multilayer decreased from 11% to 8% on annealing at 250 °C for 40 minutes. From the measured roughness and total thickness of Au layers it was found that Au preferentially intermixes with Py, which reduces the magnitude of GMR.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1667-1677"},"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)00407-M","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86144500","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":"Giant magnetoresistance of electrodeposited CoNiCu/Cu multilayers","authors":"S.Z. Hua,&nbsp;L. Salamanca-Riba ,&nbsp;L.H. Bennett,&nbsp;L.J. Swartzendruber ,&nbsp;R.D. McMichael,&nbsp;D.S. Lashmore ,&nbsp;M. Schlesinger","doi":"10.1016/0956-716X(95)00399-G","DOIUrl":"10.1016/0956-716X(95)00399-G","url":null,"abstract":"<div><p>Giant magnetoresistance (GMR) has been studied in electrodeposited CoNiCu/Cu multilayers. The value of the change of resistance with field, ΔR, is almost constant when the temperature is lowered to 15 K, whereas the <span><math><mtext>GMR = </mtext><mtext>ΔR</mtext><mtext>R</mtext></math></span> is, of course, increased. The magnetic field dependence is unchanged with temperature, demonstrating that the GMR is not thermally activated. Lorentz electron microscopy was used to investigate the nature of the magnetic domains. The layers are antiferromagnetically coupled, and the domains extend without interruption for ≈ 200 nm along the layers.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1643-1646"},"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)00399-G","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88658501","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":"Microstructural influence on magnetic properties and giant magnetoresistance of melt-spun gold-cobalt","authors":"A. Hütten ,&nbsp;J. Bernardi ,&nbsp;S. Friedrichs ,&nbsp;G. Thomas ,&nbsp;Lluis Balcells","doi":"10.1016/0956-716X(95)00401-G","DOIUrl":"10.1016/0956-716X(95)00401-G","url":null,"abstract":"<div><p>Microstructural influence on saturation magnetization, remanence, coercivity and giant magnetoresistance (GMR) of melt-spun Au_1−x-Co_x, (x = 0.65 and 0.284) ribbons in the as-quenched state and subsequently annealed at 480 °C has been investigated using analytical transmission electron microscopy. The evolution of the magnetic data with annealing time was found to be determined by the sequence of the formation of Co precipitates, their volume fraction, their particle size distribution and their morphology. GMR behavior was only measured for Au_73.6Co_28.4 and is clearly caused by a lamellar eutectic with a structure similar to multilayers.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1647-1666"},"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)00401-G","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83469571","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":"Stress and strain in micro- and nano-structured interstitial magnets","authors":"R. Skomski","doi":"10.1016/0956-716X(95)00393-A","DOIUrl":"10.1016/0956-716X(95)00393-A","url":null,"abstract":"<div><p>Hooke's law is used to calculate the elastic stress and strain in interstitial magnets. Emphasis is put on spherical and plate-like Sm₂Fe₁₇N_x particles with continuous and discontinuous interstitial concentration profiles, hypothetical high-performance Sm₂Fe₁₇N_3−δ/<span><math><mtext>Fe</mtext></math></span>Co composites, and ‘natural’ multilayers such as Nd₆Fe₁₃CuH_x, where the recently discovered large anisotropic lattice expansion is shown to arise from the crystal structure.</p><p>Das Hookesche Gesetz wird benutzt, um elastische Spannungen und Dehnungen in Zwischengittermagneten zu berechnen. Hauptgegenstand der Untersuchung sind kugelförmige und flache Sm₂Fe₁₇N_x Teil-chen mit kontinuierlichen und diskontinuierlichen Zwischengitterkonzentrations-profilen, hypothetische Sm₂ Fe₁₇N_3−δ/<span><math><mtext>Fe</mtext></math></span>Co Hochleistungskomposite und natürliche Vielfachschichten wie Nd₆Fe₁₃CuH_x, deren unlängst entdeckte groβe anisotrope Gitteraufweitung auf die Kristallstruktur zurückgeführt wird.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1831-1839"},"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)00393-A","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79386380","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":"A simple closed-form expression for the X-ray reflectivity from multilayers with cumulative roughness","authors":"David M. Kelly ,&nbsp;Eric E. Fullerton ,&nbsp;Jacobo Santa-Maria ,&nbsp;Ivan K. Schuller","doi":"10.1016/0956-716X(95)00391-8","DOIUrl":"10.1016/0956-716X(95)00391-8","url":null,"abstract":"<div><p>We present a simple closed-form expression for the reflectivity from a multilayer which includes the effects of absorption, refraction, surface and substrate reflections but neglects dynamical effects. This expression reproduces the exact dynamical calculation except for the regions near the critical angle and for intense Bragg reflections. The expression is generalized to include cumulative interface roughness which follows a <span><math><mtext>t</mtext><msup><mi></mi><mn><mtext>1</mtext><mtext>2</mtext></mn></msup></math></span> power-law growth.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1603-1608"},"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)00391-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88769062","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":"Materials with large magnetostrains","authors":"J.R. Cullen","doi":"10.1016/0956-716X(95)04041-K","DOIUrl":"10.1016/0956-716X(95)04041-K","url":null,"abstract":"<div><p>A review is given of the basic concepts which underlie the magnetostrictive behavior of ferromagnetic materials. The microscopic, i.e., atomic and electronic properties of magnetoelastic ferromagnets are discussed, with an emphasis on anisotropic magnetostriction. The latter is defined as the change in dimension of a ferro-magnet caused by rotation of the magnetization. Formulae for length changes along a given direction in terms of the magnetization direction are derived for cubic and hexagonal crystals. Approximations for the saturation strain of polycrystalline aggregates are discussed and compared with data on cubic crystals. Results of saturation magnetostriction measurements of rare-earth compounds and alloys are reviewed and tabulated. Finally, a brief discussion is given of the relationship between lattice structure and magnetostriction.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1849-1867"},"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)04041-K","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85535827","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":"Coercivity mechanism in (CoPt) and (CoPd) multilayers","authors":"Takao Suzuki","doi":"10.1016/0956-716X(95)00519-2","DOIUrl":"10.1016/0956-716X(95)00519-2","url":null,"abstract":"<div><p>Two approaches are discussed to understand the coercivity mechanism of multilayer (<span><math><mtext>Co</mtext><mtext>Pt</mtext></math></span>) and (<span><math><mtext>Co</mtext><mtext>Pd</mtext></math></span>) films with high coercivity and high perpendicular magnetic anisotropy. One approach follows the phenomenological model proposed by Kronmüller et al^(1,2), and the other is the one based on the relaxation mechanism⁽³⁾. The first approach provides the size of the pinning region. Using the measured values of coercivity, magnetization and perpendicular magnetic anisotropy constant as a function of temperature, and assuming the exchange constant and anisotropy of a pinning region to be a half the matrix value, and zero, respectively, one obtains a few Å for a pinning size in the multilayers. The second approach is based on the dependence of apparent coercivity on sweep speed of magnetic field. It is shown that the Barkhausen volume is of the order of 10⁻¹⁸cm³ for those multilayers. The results are compared to the case of Tb₂₆(FeCo)₇₄ amorphous films.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1609-1623"},"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)00519-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85497503","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":"Mössbauer studies and correlation of coercivity with particle morphology in FeSiO2 and FeBN granular solids","authors":"G.C. Hadjipanayis ,&nbsp;A. Tsoukatos ,&nbsp;V. Papaefthymiou ,&nbsp;A. Simopoulos ,&nbsp;A. Kostikas","doi":"10.1016/0956-716X(95)00455-5","DOIUrl":"10.1016/0956-716X(95)00455-5","url":null,"abstract":"<div><p>Large differences have been observed in the coercivity values of <span><math><mtext>Fe</mtext><mtext>SiO</mtext><msub><mi></mi><mn>2</mn></msub></math></span> and <span><math><mtext>Fe</mtext><mtext>BN</mtext></math></span> granular films with the coercivities being much lower in the BN matrix. We have used Mössbauer spectroscopy in an attempt to understand the differences in the magnetic hysteresis behavior. The Mössbauer data suggest a core/shell morphology for the <span><math><mtext>Fe</mtext><mtext>SiO</mtext><msub><mi></mi><mn>2</mn></msub></math></span> films with an Fe(Fe-Si) core surrounded by an Fe-Si-O shell whose surface consists of Fe²⁺-Si-O grains. In <span><math><mtext>Fe</mtext><mtext>BN</mtext></math></span> the data indicate the presence of amorphous Fe-B particles in a BN matrix. This hypothesized particle morphology can explain the high coercivity values in SiO₂ films and the low H_c in BN because of the low anisotropy of the amorphous phase.</p></div>","PeriodicalId":101150,"journal":{"name":"Scripta Metallurgica et Materialia","volume":"33 10","pages":"Pages 1679-1686"},"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)00455-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90951583","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}