Magnetic vortex core reversal by low-field excitations
Contact: Hermann Stoll,
In micrometer-sized magnetic thin films, the magnetization typically adopts an in-plane, circular configuration known as a magnetic vortex. At the vortex core, the magnetization turns sharply out of the plane, pointing either up or down. Magnetic data storage based on this binary phenomenon is an intriguing concept, but it would require the ability to flip the vortex cores on demand. Because these structures are highly stable, very strong magnetic fields of around half a tesla (approximately one-third the field of the strongest permanent magnet) were previously thought to be necessary to accomplish this. At the ALS, a team of researchers from Germany, Belgium, and the U.S. has used time-resolved scanning transmission x-ray microscopy (STXM) to observe vortex motion and demonstrate the feasibility of using weak magnetic fields as low as 1.5 millitesla (mT) to reverse the direction of a vortex core. The observed switching mechanism, which can be understood within the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application to data storage technologies. Read more...
Publication about this research: B. Van Waeyenberge, A. Puzic, H. Stoll, K.W. Chou, T. Tyliszczak, R. Hertel, M. Fähnle, H. Brückl, K. Rott, G. Reiss, I. Neudecker, D. Weiss, C.H. Back, and G. Schütz, "Magnetic vortex core reversal by excitation with short bursts of an alternating field," Nature 444, 461 (2006).
Optical upgrades increase performance of Sector 5 beamlines
Contact: Paul Adams,
Beamlines 5.0.1, 5.0.2, and 5.0.3 have undergone a major upgrade in their optics—the most significant since their construction. During the upgrade, which was the culmination of two years of work, all of the internally water-cooled copper premirrors were replaced by slot-cooled silicon mirrors. As a part of this installation, new high-vacuum tanks with improved mirror-bending mechanisms were designed and installed.
This optical upgrade has significantly improved the performance of the Sector 5 beamlines, which use x rays from the W16 wiggler. A five- to tenfold improvement in available flux has been achieved at the side-station beamlines (5.0.1 and 5.0.3), which now generate 1.5 x 1011 photons per second at 12.4 keV. The performance of 5.0.2 (the tunable beamline) was improved by a factor of 3 to 4. It now generates 8 x 1011 photons per second at 10 keV at 400-mA ring current, which surpasses even the theoretical maximum performance of the macromolecular superbend beamlines at the ALS. The upgrade has also extended the energy range of 5.0.2 to 17 keV, enabling the routine use of shorter wavelengths and anomalously scattering elements such as bromine. This recent work has been part of a series of upgrades, started in 2004, that has increased the flux overall of all Sector 5 beamlines by a factor of 20.
John Pepper makes final adjustments to optical assembly for Sector 5 side-station beamlines.
This upgrade, funded by the ALS and Berkeley Lab, was performed by the staff of the Berkeley Center for Structural Biology, ALS Experimental Systems Group, and ALS Engineering. Those involved include Simon Morton, Jeff Dickert, and John Taylor (Berkeley Center for Structural Biology); Howard Padmore and James Glossinger (ALS Experimental Systems Group); and Rob Duarte, John Pepper, Pat McKean, and Alexis Smith-Baumann (Engineering Division).
Users benefit from restructuring of ALS Beamline Coordination Group
Contacts: Gary Krebs,
; Donna Hamamoto,
The old ALS Beamline Coordination Group has been divided into two groups, Experiment Setup Coordination, which is in the User Services Group, and Floor Operations, which is in the Operations Group. The ALS believes the two new groups working together will afford greater coverage and assistance to users in both access to and safety at the ALS. The Experimental Setup Coordination group consists of Donna Hamamoto and David Malone. They make early contact with experimenters to confirm the samples and hardware for each experiment, coordinate Experiment Safety Sheet inspections for new and returning experiments, and serve as the main point of contact for experiment-related needs. The group also provides assistance with the setup of toxic gases, ALS Chemistry Lab access, and waste disposal. Users should contact Donna (
) or David (
) anytime regarding the addition of new samples, equipment, and people to their experiments.
Experiment Setup Coordinators Donna Hamamoto (left) and David Malone (right) at Beamline 10.3.1 endstation.
Complementing and working closely with the Experiment Setup Coordinators are the Floor Operators (see "ALS Floor Operators ensure safety," ALSNews Vol. 273), whose primary function is to oversee the safety of the beamlines. Floor Operations provides beamline key enable and shielding integrity assistance and, once fully staffed, also will provide off-shift safety oversight. The Floor Operations group consists of John Pruyn (
), Matthew Abreu (
), and Davy Xu (
Safety First: Be aware of construction site boundaries
Contacts: Roger Falcone,
; Jim Floyd,
It is extremely important for all ALS staff and users to recognize the construction site boundaries of the User Support Building (USB) project. These boundaries are now very clearly marked with fencing or caution tape and signs. Only authorized individuals with hard hats, etc., are allowed into the construction zone. If you are not a part of the project, you must respect this boundary and stay out at all times. In addition to the inherent safety risk to people, unauthorized access adds risk to the project and could shut it down. Neither of these risks can be tolerated, and any individual found violating this policy will be subject to appropriate action under Berkeley Lab policy.
See "Demolition of building 10 set to begin" ALSNews Vol. 273, for more information on this construction. The Berkeley Lab Site Map provides the Building 10 demolition/USB construction location.
In Memoriam: The ALS remembers Al Baez and Jim Patel
ALBERT V. BAEZ, noted physicist, humanitarian, educator, and member of the ALS user community, died on March 20, 2007, at the age of 94. He was the father of folk singers Joan Baez and the late Mimi Farina.
Al was born in Puebla, Mexico. He received his Ph.D. from Stanford University in California. There, in 1948, he and Paul Kirkpatrick pioneered grazing incidence mirrors to focus x rays. A focusing geometry using two grazing incidence mirrors mounted perpendicular to each other is known as the Kirkpatrick-Baez geometry. Berkeley Lab's Center for X-Ray Optics pioneered the use of this system at x-ray synchrotrons. In 1993 the first beamline at the ALS (10.3.1) used a Kirkpatrick-Baez mirror system. Al was also the person who first suggested the use of Fresnel zone plates with ultraviolet light and soft x rays, and demonstrated their use in the ultraviolet. As the first director of its science-teaching division, Al worked with UNESCO from 1961 to 1967. Also, he spent a year in Baghdad building a university physics laboratory. In 1967, he wrote The New College Physics: A Spiral Approach, a physics textbook. As a life-long pacifist and Quaker, Al opposed the Vietnam War and was active in many peace and humanitarian programs. He served as president of Vivamos Mejor (Let Us Live Better), which is dedicated to improving the quality of life through science-based education and community-development projects in Latin America. "In all aspects of his life, he combined personal and professional roles as scientist, environmentalist, teacher, and humanitarian. In doing so, he nurtured and conveyed values representing mankind at its best," the Baez family said in a statement.
JAMSHED (JIM) R. PATEL, ALS user and dear colleague to many, died on March 3, 2007, at his home in Menlo Park at the age of 81.
Jim received his master's degree in mechanical engineering and Ph.D. in metallurgy in his native India. After working in the Materials Sciences Division at Bell Laboratories for many years, Jim moved to California in 1994, where he held a joint position at the ALS and SSRL/SLAC Stanford University. A Fellow of the American Physical Society, he also held numerous visiting and consulting positions at several international science institutions including the Université Pierre et Marie Curie in Paris, France; the NSLS (Brookhaven); CHESS (Cornell); and Intel Corporation in Santa Clara.
At the ALS, Jim was instrumental in developing a successful x-ray microdiffraction program at Beamline 7.3.3, providing the initial funding though his position as a consultant at Intel. He initiated many of the materials sciences applications for the beamline, including the study of electromigration-induced plasticity in interconnect test structures and strain measurements at grain and domain boundaries in superconducting alloys. Jim worked tirelessly on this project until last summer, when he became ill. Even then, he stayed active until his very last day, reading articles and writing his monograph on the technique and application of synchrotron x-ray microdiffraction. Jim was a true gentleman of science, quiet and unassuming with the keenest of intellects, but always with the time to help and encourage his colleagues. He made a deep impression on anyone who knew him, and he will be sorely missed by all.
Our thoughts go out to Al's and Jim's families and friends throughout the world.
American Physical Society awards go to Franz Himpsel and Sam Bader
FRANZ HIMPSEL has won the 2007 Davisson-Germer Prize "for pioneering investigations of the electronic structure of surfaces, interfaces, adsorbates, and nanostructures." Himpsel has been a long-time involved and dedicated ALS user. He was part of the group that argued for the establishment of the ALS, was among the team that built one of the first two undulator beamlines, and later took part in the development of a nano-NEXAFS endstation at Beamline 8.0.1. He served on the ALS Science Policy Board and was just elected to the ALS Users' Executive Committee. Himpsel is a pioneer in the field of surface science using synchrotron radiation. After receiving his Ph.D. in physics from the University of Munich, he spent almost two decades at IBM Research before joining the University of Wisconsin-Madison as a physics professor in 1995. He is also a long-time user of the Synchrotron Radiation Center (SRC) in Madison and served as its Scientific Director from 1997 to 2002. More information can be found on the American Physical Society Web site.
SAM BADER, member and past chair of the ALS Scientific Advisory Committee, received the 2007 David Adler Lectureship Award for his "spirited lectures, writing and experimental research in the area of nanomagnetism, magnetic films, multilayers and surfaces of metallic systems, including championing the surface magneto-optic Kerr effect approach." The award was presented at the March meeting of the American Physical Society (APS), where Bader gave an invited talk in the awards session of the Division of Materials Physics. Bader is an Argonne Distinguished Fellow and currently serves as Chief Scientist of the new Center for Nanoscale Materials and as Associate Division Director and group leader in Argonne's Materials Science Division. He is a Senior Fellow and Deputy Director of the University of Chicago-Argonne Consortium for Nanoscience and holds adjunct professorships in the Department of Materials Science and Engineering at the University of Illinois, Urbana-Champaign, and in the Department of Physics and Astronomy at Northwestern University. He received the 1992 DOE-BES Award in Solid State Physics for work on coupled magnetic layers, the 1994 University of Chicago Award for Distinguished Performance at Argonne, and the 2001 AVS Thornton Award for "surface and thin film magnetism." More information can be found on the American Physical Society Web site.
9/11 dust analyzed by ALS user Tom Cahill for Esquire magaine
University of California, Davis, professor and ALS user Tom Cahill is featured in the April edition of Esquire magazine. He was asked by writer Eric Gillin to analyze the dust particles on a messenger bag that Gillin was carrying in downtown New York when the World Trade Center Towers fell on September 11, 2001. After storing the bag for five years, Gillin's curiosity about the contents of the dust led to Dr. Cahill, UC Davis, and the ALS. Read the full story online at the Esquire Web site or download the PDF.
Register now for Coherence 2007
Contact: Janos Kirz,
Anyone planning on attending the Coherence 2007 Conference at the Asilomar Conference Center, June 25–27, is encouraged to register by Sunday, April 15, to take advantage of reduced registration fees. April 15 is also the deadline for reserving accommodations at Asilomar. The conference, fourth in a series, will be devoted to coherent x-ray physics. Three topics will be featured: imaging with coherent x rays, dynamics via photon correlation, and opportunities with new sources. For more information about the meeting, including a preliminary agenda, invited speakers, contacts, and tourism opportunities in and around the Monterey peninsula, see the Coherence 2007 Web site.