Georg LauhoffIBM · Magnetic Tape Storage
Georg Lauhoff
Ph.D., M.Phil., Dipl.-Phys. M.B.A.
About
68
Publications
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Introduction
Engineer and Physicist in the fields of Material Science
Product Design, Process Development and Test Engineering
I have served in a wide range of responsibility spanning from carrying out research of new materials to the designing, product developing from the initial stage to mass production.
Additional affiliations
December 2021 - present
December 2009 - November 2020
August 2006 - December 2009
Samsung Electronics R& D Center
Position
- Engineer
Description
- Product Design, Component Integration
Education
October 2015 - May 2020
October 1995 - May 1998
October 1994 - September 1995
Publications
Publications (68)
We report on the ferrimagnetic superlattice ordering in epitaxial tau-MnAl/Co superlattices on GaAs. For ultrathin Co layers (3.5-7 Å), both the ferromagnetic tau MnAl and Co layers display a large perpendicular magnetic anisotropy together with an antiferromagnetic interface exchange coupling. As a result, an abrupt transition from the ferromagnet...
The understanding of magnetic properties such as the magnetocrystalline
anisotropy (MCA) in device applications, which usually involve more than
one magnetic element, depends to a large extend on the element-resolved
separation of orbital and spin contributions to the total magnetic
moment. Magnetic circular x-ray dichroism is to date the only tech...
In this paper, we review some of the key concepts in ultrathin film magnetism which underpin nanomagnetism. We survey the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic mom...
The structural and magnetic properties of thin Ni films grown on Cu/Fe/MgO(001)
and Cu/MgO(001) buffer layers are investigated and compared to those grown
on Cu/Si(001). The use of an Fe seed layer a few monolayers thick leads to the
epitaxial growth of high surface quality Cu(001) buffer layers on MgO(001),
while Cu growth on the bare MgO(001) sub...
The field dependence of activation volume (Va) is determined by four different methods for longitudinal recording media. For two methods using the irreversible magnetization, Va increases with reversing fields up to the coercivity (Hc). The Va determined from the time dependence of the total magnetization, which includes the reversible magnetizatio...
Dieses Buch befasst sich mit der die Praxis, große Datenbanken zu analysieren, um neue Informationen zu generieren was man auf Englisch und auf Deutsch als Data-Mining nennt. So schürft man wie in einer Goldmine neue Goldschätze Das beschreibenden Data-Mining (deskriptiven Data Mining) , ist ein Aspekt des Data-Mining. Wie im Vorwort erwähnt, befas...
Mit der RFM-Analyse (Recency, Frequency, and Monetary) wird versucht, Kunden zu identifizieren, die mit höherer Wahrscheinlichkeit auf neue Angebote reagieren. Das Pareto Prinzip besagt, das 80 % des Verkaufes von 20 % der Kunden kommt. Darum ist es so wichtig, diese Kunden zu identifizieren. In der RFM Analyse werde diese mit drei Parametern. Doch...
Wissensentdeckung ist das Bemühen, Informationen aus Daten zu finden. Aus heutiger Sicht ist es die Anwendung von Werkzeugen (aus der Statistik und der künstlichen Intelligenz), um interessante Muster aus Daten zu extrahieren, die in großen Datenbanken gespeichert sind. Interessant bedeutet hier nicht-triviales, implizites, bisher unbekanntes und l...
Daten und Informationen sind wichtige Ressourcen, die in modernen Unternehmen verwaltet werden müssen. Business Analytics bezieht sich auf die Fähigkeiten, Technologien, Anwendungen und Praktiken zur Erkundung und Untersuchung vergangener Unternehmensleistungen, um Erkenntnisse zu gewinnen und die Unternehmensplanung zu unterstützen. Der Schwerpunk...
Bei der Link-Analyse werden die Beziehungen zwischen Entitäten in einem Netzwerk untersucht. Sie sind in vielen Kontexten interessant, z. B. bei der Analyse sozialer Netzwerke (Knoke und Yang, Social network analysis, 2nd edn. Sage Publications, Thousand Oaks, CA 2008), die zur Messung sozialer Beziehungen, einschließlich sozialer Medien und Kollab...
Wir leben in einem Zeitalter der allgegenwärtigen Information, in dem Unmengen von Daten zu praktisch jedem Aspekt des Lebens verfügbar sind. Unser tägliches Leben kann durch Fitbit zur Überwachung gesundheitsbezogener Daten unterstützt werden, durch Sensorsysteme zur Überwachung unserer Häuser und zur Überprüfung derjenigen, die an unsere Haustür...
Die Assoziationsanalyse bezeichnet die Suche nach Korrelationen zwischen gemeinsam auftretenden Dingen. Der Zweck einer Assoziationsanalyse besteht also darin, Items z. B. einzelne Artikel eines Warenkorbs zu ermitteln, die das Auftreten anderer Waren innerhalb einer Transaktion implizieren. Mit Assoziationsregeln wird versucht, Kombinationen von D...
Dieses Kapitel behandelt eine Reihe von Aspekten der Clusteranalyse. Zunächst wird das Clustering von Hand anhand von standardisierten Daten vorgestellt. Damit soll gezeigt werden, wie grundlegende Algorithmen funktionieren. Der zweite Abschnitt zeigt, wie die Software mit diesen standardisierten Daten arbeitet. Im dritten Abschnitt wird die Cluste...
Link analysis considers the relationship between entities in a network. They are interesting in many contexts, to include social network analysis (Knoke and Yang, Social network analysis, 2nd edn. Sage Publications, Thousand Oaks, CA, 2008) which has been used to measure social relationships, to include social media and collaboration networks. Peop...
Knowledge discovery is the effort to find information from data. In contemporary terms, it is the application of tools (from statistics and from artificial intelligence) to extract interesting patterns from data stored in large databases. Here interesting means non-trivial, implicit, previously unknown, and easily understood and described knowledge...
Association rules seek to identify combinations of things that frequently occur together (affinity analysis). This is also the basis of market basket analysis, which we discussed in terms of correlation and Jaccard ratios. Association rules take things a step further by applying a form of machine learning, the most common of which is the apriori al...
Data and information are important resources to be managed in modern organizations. Business analytics refers to the skills, technologies, applications and practices for exploration and investigation of past business performance to gain insight and aid business planning. The focus is on developing new insights and understanding based on data and st...
This chapter covers a number of aspects of cluster analysis. Initially, it presents clustering manually, using standardized data.
This book addresses descriptive analytics, an initial aspect of data mining. As stated in the preface, it looks at various forms of statistics to gain understanding of what has happened in whatever field is being studied. The book begins with a chapter on knowledge management, seeking to provide a context of analytics in the overall framework of in...
We live in an era of ubiquitous information, with masses of data available concerning practically every aspect of life. Our daily lives can be supported with fitbits to monitor health-related data, with sensor systems to monitor our homes and screen those who come to our front door, to monitor our automobiles at the same level that used to be appli...
Recency, Frequency, and Monetary (RFM) analysis seeks to identify customers who are more likely to respond to new offers. While lift looks at the static measure of response to a particular campaign, RFM keeps track of customer transactions by time, by frequency, and by amount.
This book provides an overview of data mining methods demonstrated by software. Knowledge management involves application of human knowledge (epistemology) with the technological advances of our current society (computer systems) and big data, both in terms of collecting data and in analyzing it. We see three types of analytic tools. Descriptive an...
τ MnAl/Co superlattices are grown epitaxially on GaAs (100) substrates by molecular beam epitaxy. High angle XRD spectra are analysed and indicate that good structural quality is achieved. The behaviour of the superlattice upon annealing is described and compared with in-plane and out of plane magnetization data. Extraordinary hall effect measureme...
PMR recording areal density in latest generation drives is at approximately 500 Gb/in2. As expected, the four to five-fold increase in recording density since the introduction of PMR technology in 2005 has been made possible by many enabling technologies in heads, media, channels, etc. Surprisingly, as the size of the recording bit has shrunk in ac...
The effect of the interface on the magnetic moment of Cu/Co,Ni/Cu/Si(0 0 1) epitaxial structures was studied by polarised neutron reflection (PNR). The structure consists of a specially designed three-step sample (single 60 Å Ni and 10 Å Co films and a 10 Å Co/60 Å Ni bilayer) grown under the same conditions in order to eliminate variations in the...
We report polar magneto-optical Kerr effect studies of Cu spacer layer on the perpendicular magnetic anisotropy in 70 Å Ni/Cu wedged/70 Å Ni structures. With increasing Cu thickness, the magnetic easy axis of the top Ni layer continuously changes to the direction perpendicular to the surface. This results from the gradual strain relaxation of the C...
A study of the magnetic and structural properties of (Co-Ni)3Pt alloy thin films epitaxially grown onto Al2O3(00.1) substrates has been carried out. The (CoNi)3Pt and Ni3Pt films deposited in a temperature range of 300-450 °C show a partial superlattice ordering. The perpendicular magnetic anisotropy Ku is found to increase with order parameter S....
Summary form only given. A close correlation between the intrinsic perpendicular magnetic anisotropy (Ku) and order parameter in Co3Pt ordered alloy thin film onto Al2O3 [001] was previously reported. In order to understand in detail the physical origin of the Ku, the present study investigates the compositional dependence of Ku of ordered (Co-Ni)3...
The intrinsic perpendicular magnetic anisotropy constant K<sub>u </sub> of (Co<sub>100-x</sub>Fe<sub>x</sub>)<sub>50</sub>Pt<sub>50 </sub>(0⩽×⩽100) alloy thin films is determined at room temperature. It is found to increase with order parameter S, and decrease with the tetragonality c/a for all compositions. The estimated K<sub>u</sub> valu...
Brillouin light scattering measurements of spin-wave frequencies in an exchange coupled ferromagnet/antiferromagnet epitaxial Co/CoO bilayer are reported. A striking temperature dependence of the measured spin-wave frequencies in the cobalt layer in the range 77–300 K was observed which has been demonstrated to be due to exchange coupling to the ul...
We have studied the effect of the Cu capping thickness (in the range 20⩽tCu ⩽180Å) on the magnetic and structural properties of ultrathin FCC 40Å Ni/Cu(001) films by means of magneto-optic Kerr effect (MOKE) magnetometry, polarised neutron reflection (PNR) and grazing incidence X-ray surface diffraction (GID) measurements. MOKE measurements show th...
First, a brief review of thermal decay of magnetization is given. Discussions on activation volume are presented in detail for longitudinal recording media. It is noted that the activation volume estimated based on waiting time methods is found to decrease with increasing reversing field for all the media under consideration. This result suggests t...
We report Brillouin light scattering measurements of spin-wave
frequencies in exchange coupled ferromagnet (FM)/antiferromagnet (AF)
epitaxial Co/CoO bilayer structures. The ultrathin (7 Å) CoO layer
perturbs the Co layer spin-wave frequencies and so permits a study of
the influence of the AF CoO layer at the interface, when the
unidirectional anis...
A study of magnetic and structural properties of ( Co <sub>x</sub> Fe <sub>100-x</sub>)<sub>50</sub> (0≦x≦100) alloy thin films as functions of composition and substrate deposition-temperature T<sub>s</sub> is carried out. The intrinsic perpendicular magnetic anisotropy K<sub>u</sub> starts to increase with deposition temperature T<sub>s</sub> for...
The thermal activation volume (VA) is studied for CoCrPtTa longitudinal magnetic recording media. VA is found to strongly increase for smaller reversing fields. This trend is also continued in small positive applied fields. The activation area (SA) at the same reversing fields are found to be in reasonable agreement to each other for different medi...
We report that for epitaxial Cu/Ni60Cu40/Cu(001)
and for Cu/Ni/Cu(001) structures, the in-plane lattice parameter
(ain) for Cu increases with increasing Cu overlayer
thickness. For the Cu/Ni(30 Å)/Cu/Ni/Cu(001) structures, the value
of ain of the 30-Å Ni film directly depends on
ain of the Cu underlayer. Magneto-optic Kerr effect
measurements on a...
Atomic-scale Surface Science Research Center Department of Physics Yonsei University Seoul 120-74 Korea; J. A. [email protected]
/* */ The effect of strain on the magnetic anisotropy of epitaxial Co/Ni/Cu/Si(001) structures was studied using polar magneto-optic Kerr effect (MOKE) niagnetometry and reflection high energy electron diffraction (RHEED)...
The relation between the perpendicular magnetic anisotropy
constant K<sub>u</sub> and the order parameter S of the Co<sub>3</sub>Pt
ordered phase is examined. The ordering process is suggested to be
governed by a surface diffusion based on the activation energy obtained
and annealing experiments. Lowering the deposition rate shows
significant impro...
For epitaxial Cu/Ni/Cu/Ni60Cu40/Cu(001) and Cu/30 Å Ni/Cu/Ni/Cu(001) structures, the in-plane lattice parameter of the Cu spacer layer is found to increase with its thickness. The Ni in-plane lattice parameter becomes larger with increasing Cu spacer thickness. Cu/Ni/Cu/Ni60Cu40(001) structures show an increase in the magneto-elastic anisotropy wit...
Polar magneto-optic Kerr effect (MOKE) measurements on an epitaxial Cu/Co (23 Å)/Cu (0-49 Å)/Ni (53 Å)/Cu/Si(001) structure reveal that the Ni magnetization is aligned in plane for zero Cu spacer layer thickness and becomes increasingly aligned out of plane with increasing Cu spacer layer thickness, whereas an in-plane remanent magnetization for Co...
We studied layer selectively the magnetic moments on a Cu/9 Å Co/50 Å Ni/Cu/Si(001) and a Cu/50 Å Ni/Cu/Si(001) structure using polarized neutron reflection. The magnetic moments for the Cu/Co/Ni/Cu structure are 1.70+/-0.20 muB and 0.57+/-0.05muB for the Co and Ni, respectively, and within error the same as the relevant bulk magnetic moments at ro...
We report Brillouin light scattering measurements of spin-wave frequencies in an exchange coupled ferromagnet (FM)/antiferromagnet (AF) epitaxial fcc Co/CoO bilayer structure. A striking temperature dependence of the measured frequencies in the cobalt layer in the range 77 to 300K was observed and has been demonstrated to be due to exchange couplin...
Perpendicular magnetic anisotropy (PMA) up to 6.15±1.25Å Co thickness is found for ferromagnetically coupled epitaxial Co/60Å Ni/Cu/Si(001) structures. Polarized neutron reflection measurements on a Cu/9ÅCo/Ni/Cu(001) structure yield almost bulk like magnetic moments at room-temperature of 1.70±0.20μB and 0.57±0.05μB for Co and Ni, respectively. Ma...
Polar magneto-optic Kerr effect (MOKE) measurements on epitaxial Cu/22ACo/0-49Å Cu/53Å Ni/Cu/Si(001) structures reveal that the Ni magnetisation is aligned in-plane for zero Cu spacer layer thickness and becomes increasingly aligned out-of plane with increasing Cu spacer layer thickness, whereas an in-plane remanence for Co is always observed. Pola...
The magneto-optical activity in the range from 1.4 to 6.8 eV for hcp Co 3 Pt films deposited onto Al 2 O 3 (0001) with different degree of the ordering is presented. An increasing chemical ordering, evidenced by X-ray and electron diffraction measurements, is accompanied by a change in the magneto-optical spectra in a characteristic peak at around...
This paper reports on the structural and magnetic properties of
τMnAl/Co superlattices epitaxially grown on AlAs/GaAs by Molecular
Beam Epitaxy. In τMnAl/Co superlattices with Co layer thickness
<8 Å, a strong antiferromagnetic coupling between the
ferromagnetic τMnAl and Co layers is found, as well as the presence
of a large perpendicular magnetic...
We have studied the effect of Co overlayers (0–12 Å) on a Ni (60 Å)/Cu (1000 Å)/Si (0 0 1) film structure. Epitaxial growth was confirmed by reflection high-energy electron diffraction. Magneto-optic Kerr effect and X-ray magnetic circular dichroism (XMCD) measurements show a transition from an out-of plane to an in-plane easy axis with increasing...
We have studied the transition from perpendicular to in-plane magnetization in a ferromagnetically coupled epitaxial Co/Ni/Cu(001) structure. Perpendicular magnetic anisotropy (PMA) up to 6+/-1.5 Å Co thickness is observed. The value of the uniaxial Co volume anisotropy (KCoV), which comes entirely from the shape anisotropy contribution, is explain...
A step wedged structure of the form 30 Å Cu/50 Å Ni/hÅ Cu/Si(0 0 1) () grown by MBE has been characterised by in situ RHEED and ex situ polar MOKE magnetometry and MOKE microscopy. The magnetisation reversal process was investigated through measurements of hysteresis loops, magnetisation relaxation and domain images. The sample exhibits a strong ma...
We discuss the application of polarised neutron reflection to layer selective vector magnetometry measurements in thin magnetic films. To illustrate the application of PNR, we review recent measurements of the absolute moment in X/Fe/Ag(001) structures with X = Pd, Ag, Au and Cu and compare the results with the predictions based on theoretical calc...
We have studied the magnetic moment and in-plane strain in epitaxial Cu/Ni/Cu/Si(100) structures by varying both the Ni and Cu buffer layer thickness. We find a sharp reduction in magnetic moment with increasing Ni lattice strain. Our structural and temperature-dependent studies exclude interdiffusion, interface roughness, and a decreased Curie tem...
Systematic measurements of the magnetic moment per Ni atom in Cu/Ni/Cu/Si(001) structures have been made using polarized neutron reflection (PNR) for Ni thicknesses in the range 30Å<t<400Å at room temperature. We find a dramatic reduction in the magnetic moment per atom for t<100 Å and near bulk values above 100 Å. These results are corroborated by...
We have studied the variation of the strain and the magnetic moment in epitaxial fct Ni(001) film structures using a combination of reflection high energy electron diffraction (RHEED) and x-ray magnetic circular dichroism. A 30 Å Cu/Ni step-wedge (30, 60, 90, and 150 Å)/600 Å Cu buffer/Si(001) structure has been used to study the Ni thickness-depen...
We have directly compared the values of the magnetic moment obtained from x-ray magnetic circular dichroism (XMCD) measurements with those obtained from polarized neutron reflection (PNR) measurements on strained Ni films grown on Cu(001)/Si(001). The PNR measurements show that the absolute magnetic moments differ from that of bulk Ni. We find agre...
We report the evolution of the magnetoresistance (MR) and magnetization behavior of Ni30Fe20 wire arrays as the width (w) is reduced from 200 to 0.3 mu m. At around 1.5 mu m width, the hysteretic behavior seen in continuous films shows the near reversible behavior characteristic of spin rotation processes. At low field (H<M(s)), the anisotropic mag...
