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Dr. Laurence L. Henry's Research Interest

 

The Electron Transport and Magnetic Properties of Materials (ETMPM) Laboratory

A solid state physics/materials sciences research laboratory

Department of Physics

Southern University and A&M College, Baton Rouge, LA

Principal Investigator: Dr. Laurence Henry,*

"Electron Transport and Magnetic Properties of Materials"

 

Research Interests and Activities:

Research interests include electron transport and magnetic properties of materials (bulk, thin films, thin metallic heterostructures, and alloys). The interest also extends to superconductivity and the new high temperature superconductors. Current and recent research activity includes studying the magnetic and electron transport properties in thin film ferromagnetic (F)/normal (N) multilayers and perovskite-type alloys. These studies are important to understanding Giant Magnetoresistance (GMR) in multilayers and Colossal Magnetoresistance (CMR) in R 1-x A x MnO 3 (R= trivalent rare earth atoms and A = divalent alkaline earth atoms) alloys. Our present focus is directed toward investigating the magnetic and electron transport properties in the manganese oxide alloys. The research activities include alloy sample fabrication using solid state reaction and "wet chemistry" techniques, and magnetic and electron current (I) - voltage (V) measurements at temperatures up to 320 K, and in magnetic fields up to 5 Tesla. Sample composition determinations are done using scanning electron microscopy, and x-ray diffraction techniques. Additional structural analysis is possible using XANES and EXAFS techniques at a nearby synchrotron radiation facility (CAMD, see the information below).

Equipment and Facilities

The Electron Transport and Magnetic Properties of Materials (ETMPM) laboratory houses a "state of the art" commercial SQUID magnetometer (Quantum Design Inc., model MPMS 5S) capable of measurements in magnetic fields up to 5 Tesla and temperatures ranging from 1.9 K to above room temperature. Additional equipment includes sensitive current-voltage measurements systems (Keithley nanovolt meters and constant current sources). The lab has equipment for fabricating ceramic samples (a high temperature tubular furnace capable of temperatures to near 1700 degrees Celsius and an annealing tubular furnace). Magnetotransport measurements are performed using a special sample holder and the superconducting magnet in the magnetometer. The lab is currently awaiting installation of a fully computerized system for performing heat capacity measurements. Additional structural and compositional characterization techniques are performed at facilities at nearby Louisiana State University, and the Center for Advanced Microstructures and Devices (CAMD) 1.2 - 1.5 GeV synchrotron radiation facility. Thin films and multilayer samples are fabricated by a "sputtering" technique by a research group at Michigan State University. Dr. Henry has also developed a research oriented course (PHYS 526) on materials characterization techniques using magnetic measurements and I-V techniques, and he is presently in the process of developing another research oriented course that has as its focus materials characterization using heat capacity techniques. These courses enhance the research preparedness of the students.

Research Projects (Funded, and MS degree theses directed)

Research projects under Dr. Henry's direction at SUBR that have been completed, or is in progress:

Magnetic and Structural Properties of Some Magnetic Thin Films, Multilayers, and Perovskite-Type Alloys.

[Completed in 1999. Funding agency: LEQSF, at $83,438 (24 mths).]

A Study of the relationship Between Structure, and Magnetic and Electron Transport Properties in R1-xAxMnO3 Alloys.

[Funded: $238,892/ three yrs (1998-2001). Funding agency: NASA]

A major educational project under Dr. Henry's direction that is in progress is:

An Integrated Theory and laboratory Learning Experience: A Calorimetry Lab.

[Funded $144,583/ two yrs., (1999-2001). Funding agency: NASA]

MS degree student thesis work that has been completed under Dr. Henry's direction or is currently being directed by Dr. Henry:

An Investigation of the Relationship Between Structure and Electron Transport in

La1-x(Ca1-ySry)x(MnO 2 ) d MS degree thesis (Ms. Lashondria Dixon, completed July 1998)

An Investigation of the Magnetic and Electron Transport Properties in Ni 3 Al, and Ni 3 Al (Boron Doped), Thin Films. MS degree thesis (Mr. Edward Patterson, completed December 1998).

A Structural and Magnetic Investigation of some Ni/Ag/Ni Thin Film "Sandwiches". MS degree thesis (Ms. Watasha Wade, work in progress)

An Investigation of the Current In Plane (CIP) Magnetoresistance of Sputtered [(Co + 10%Cu)/Cu] N Multilayers. MS degree thesis (Mr. Jeremy J. Jackson, work in progress).

Research support is currently from NASA, and the MS Program in Applied Physics at Southern University.

Selected Publications

Perpendicular Interface Resistances in Sputtered Ag/Cu, Ag/Au, and Au/Cu Multilayers . L. L. Henry , Q. Yang, P. Holody, R. Loloee, W. P. Pratt Jr., and J. Bass. Rev. B. 54 , 12336 (1996).

How Predictable is the Current Perpendicular to Plane Magnetoresistance? (Invited). W. P. Pratt, Jr., Q. Yang, L. L. Henry , P. Holody, W. -C. Chiang, P. A. Schroeder, J. Bass. Proceedings of the 40th Annual Conference on Magnetism and Magnetic Materials, J. Appl. Phys. 79 , 6129 (1996).

Resistivities of Sputtered Ag(3.3 nm)/Cu(tCu), Ag(3.3 nm)/Au(tAu), and Ni(4.2 nm)/Co(tCo) Multilayers at 4-5 and 295 K. L. Henry , M. Oonk, R, Loloee, Q. Yang, W.-C. Chiang, W. P. Pratt, Jr., and J. Bass. Proceedings of the 40th Annual Conference on Magnetism and Magnetic Materials, J. Appl. Phys. 79 , 6129 (1996).

Studying Spin-Dependent Scattering in Magnetic Multilayers by Means of Perpendicular (CPP) Magnetoresistance Measurements. J. Bass, P. A. Schroeder, W. P. Pratt, Jr., S.-F. Lee, Q. Yang, P. Holody, L. L. Henry , and R. Loloee. Mat. Sci. & Eng. B31 , 77 (1995).

Prediction and Measurement of Perpendicular (CPP) Giant Magnetoresistance of Co/Cu/Ni84Fe16/Cu Multilayers. Q. Yang, P. Holody, S.-F. Lee, L. L. Henry , R. Loloee, P. A. Schroeder, W. P. Pratt Jr., and J. Bass. Phys.Rev. B, 51 , Feb. (1995).

Spin Diffusion Length and Giant Magnetoresistance at Low Temperatures . Q. Yang, P. Holody, S.-F. Lee, L. L. Henry , R. Loloee, P. A. Schroeder, W. P. Pratt Jr., and J. Bass. Phys. Rev. Lett. 72 , 3274 (1994).

Calorimetric Study of Magnetic Order in Ho(Co,Rh)2 Alloys. L. L. Henry , L. E. Wenger, G. D. Khattak and A. Tari. Phys. Rev. B, 43 , 689 (1991).

Presentations (The first author was the presenter at the conference, except as indicated as "Joint presentation".)

Utilizing the Internet for two Web Based Courses. R. Tashakkori and L. L. Henry . Presented at the Conference on Teaching in Higher Education (THE), Louisiana State University, Baton Rouge, LA. April 20, 1999. (Joint presentation)

Some Preliminary Magnetization and Resistance Results From Boron Doped Ni3Al Thin Films . L. L. Henry . Presentation at the Symposium on Magnetic Materials at Southern University, Baton Rouge, LA. July 16, 1998.

An Integrated Theory and Experiment Learning Experience: Magnetic Characterization of Materials . L. L. Henry , Presented at the Conference on Teaching in Higher Education (THE), Louisiana State University, Baton Rouge, LA. April 20, 1998.

Resistivities of Sputtered Ag(3.3 nm)/Cu(tCu), Ag(3.3 nm)/Au(tAu), and Ni(4.2 nm)/Co(tCo) Multilayers at 4-5 and 295 K. L. Henry , M. Oonk, R, Loloee, Q. Yang, W.-C. Chiang, W. P. Pratt, Jr., and J. Bass. Proceedings of the 40th Annual Conference on Magnetism and Magnetic Materials, J. Appl. Phys. 79 , 6129 (1996).

Superconducting(S) / Ferromagnetic(F) and Superconducting(S) / Spin-Glass(SG) Interface Resistances. L. L. Henry , Q. Yang, C. Fierz, S. -F. Lee, P. A. Schroeder, W. P. Pratt Jr., and J. Bass. Bull. Am. Phys. Soc. 39 , No 1, 765 (1994).

Isolating the Spin-Flip Diffusion Length From Low Temperatures Giant Magnetoresistance (MR) Measurements on Magnetic Multilayers. Q. Yang, P. Holody, S.-F. Lee, L. L. Henry , R. Loloee, P. A. Schroeder, W. P. Pratt Jr., and J. Bass. Bull. Am. Phys. Soc. 39 , No 1, (1994).

Anomalous Magnetic Behavior in Melt-Textured YBaCuO. L. L. Henry , M. S. M. Minhaj, J. Obien, L. E. Wenger and J. T. Chen. Bull. Am. Phys. Soc. 36 , No 3, (1991).

Microstructure and Physical Properties of BiSrCaCuO Materials. E. M. Logothetis, R. E. Soltis, S. Shinozaki, R. Ager, W. Donlon, W. Win, L. Henry . Bull. Am. Phys. Soc. 34 , No 3 , 73, (1989).

*Laurence L. Henry, Ph.D. Physics (Solid State - experimental), Wayne State University, Detroit, MI. (1991)

Department of Physics

Southern University and A&M College

Baton Rouge, LA 70813

e-mail: i9987@aol.com

voice: (225) 771-4130

 

Selected Publications: Click Here


 
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