| Biography: Daniel T. Pierce
Daniel T. Pierce
Daniel Pierce received his B.S. degree in Physics from Stanford University in 1962. After two years teaching physics at Tri-Chandra College in Kathmandu, Nepal with the U.S. Peace Corps, he returned to Wesleyan University in Connecticut where he received an M.A. in Physics in 1966. He received his Ph.D. in Applied Physics from Stanford University in 1970, for work involving photoemission measurements of the electronic structure of Ni above and below the Curie temperature and calculations of the corresponding energy distribution curves from an interpolated band structure. He remained with Prof. W.E. Spicer at Stanford for a year as a postdoctoral researcher to study amorphous semiconductors and help develop plans for the Stanford Synchrotron Radiation Laboratory.
In 1971, Dr. Pierce joined the group of Prof. H.C. Siegmann at the Eidgenossische Technische Hochschule (ETH) in Zurich to investigate magnetic materials using spin-polarized photoemission. He took part in studies of the spin-dependent electronic structure of magnetic transition metals and magnetic insulators and ferrites such as EuO and Fe304. He shared in the discovery that electrons photoemitted from negative electron affinity GaAs with circularly polarized light are highly spin polarized. This result is the basis of the GaAs spin-polarized electron source that is the most widely used source of spin-polarized electrons for investigations in atomic, solid state, and high energy physics.
Dr. Pierce joined the NIST (National Institute of Standards and Technology, formerly National Bureau of Standards) in 1975. Pierce and R.I. Celotta, with whom he shares this award, and colleagues at NIST developed the GaAs spin-polarized electron source for low-energy applications. Polarized electron scattering was used to investigate symmetry relations in low energy electron diffraction from surfaces, where the spin dependence arises from the spin-orbit interaction. The spin dependence measured for surface resonance scattering in low-energy Rydberg states has led to a better model of the surface potential barrier in W(100).
Recognizing the power of spin polarized electrons for studying surface magnetism, Pierce, Celotta, and their collaborators carried out the first polarized low energy-electron diffraction measurements from a magnetic material, the Ni(110) surface. The results showed the size of the spin dependent scattering due to the exchange interaction and indicated the sensitivity of surface magnetism to adsorbates. These measurements established a new, sensitive means to measure the degree of surface magnetic order. Polarized electron scattering from ferromagnetic glasses confirmed the theoretical predictions that the temperature dependence of the surface magnetization at low temperatures should have the same power law of the bulk, but found a larger prefactor than predicted which can be explained by a reduced exchange coupling of the surface to the bulk.
The GaAs polarized electron source at NIST was used to make the first spin polarized inverse photoemission measurements demonstrating that information can be obtained about the spin dependent electronic structure of the unfilled states in a ferromagnet. This information, complementary to that from spin polarized photoemission, is of particular interest because the 3d holes play key role in transition metal magnetism. Spin polarized inverse photoemission measurements revealed how chemisorption induces changes in surface magnetism.
Energy- and spin-resolved secondary electron measurements carried out at NIST showed that a ferromagnetic metal yields an abundance of highly polarized secondary electrons. This made clear the possibility of measuring the polarization of secondary electrons generated in a scanning electron microscope to achieve high resolution imaging of surface magnetization. The technique, which has come to be known as scanning electron microscopy with polarization analysis or SEMPA, has been used to investigate a variety of fundamental and technologically important aspects of magnetic microstructure including the influence of the surface on domain wall microstructure, domains in Ni-Fe memory elements and thin film recording media, and the oscillatory exchange coupling of two magnetic layers through a nonmagnetic spacer layer. Dr. Pierce's present research interests include the application of SEMPA to surface and thin film magnetism, the characterization and understanding of thin film growth using the STM, and the achievement of spin dependent magnetic contrast in STM measurements.
Dr. Pierce has authored or co-authored 150 publications including several book chapters and review articles. He has three joint patents which include GaAs polarized electron source and two types of spin analyzer. He has shared in two IR-100 Awards, the Department of Commerce Silver and Gold Medals, the NIST E.U. Condon and William P. Slichter Awards, and the Washington Academy of Science Distinguished Achievement Award. Dr. Pierce wishes to acknowledge the supportive research environment he has benefited from at Stanford, ETH and NIST, and the fruitful collaborations he has enjoyed throughout his career with many talented colleagues from these and other laboratories. Pierce is a NIST Fellow and a Fellow of the American Physical Society.