Research Interests of R. Schumann


Publications

Mixed Valence, Strong Correlation

R. Schumann, K. Elk
"On the Thermopower and Thermal Conductivity of the Periodic Anderson Model"
phys.stat.sol.(b) 119 (1983)221

R. Schumann, K. Elk
"Über analytische Eigenschaften der Einteilchengreenfunktionen in einem Zwei-Band-Modell"
Annalen der Physik 40 (1983)347

R. Schumann
"Temperature dependence of the Thermopower of the Periodic Anderson Model"
phys.stat.sol.(b) 120 (1983)K183

R. Schumann, K. Elk
"Zur Suszeptibilität im Periodischen Anderson Modell"
Wiss.Zschr.d.HfV 31(1984)621

R. Schumann, E. Heiner
"Transformations of the Hubbard Interaction to Quadratic Forms"
Phys.lett. A 134(1988)202

R. Schumann
"On the Functional Integral Method applied to models with Hubbard Type Interaction"
Phys.lett. A 138(1989)151

R. Schumann
"Relation between Spin and Quasispin in Models with Hubbard Type Interaction"
Proc. 7th Intern.Sem.Magn., Rathewalde 1989

R. Hayn, R. Schumann, V. Yu. Yushanghai
"Metal Insulator Transition in the Emery Model"
Proc. 20th Symp. of Electronic Structure, Dresden, 1990

R. Hayn, R. Schumann
"The Charge Transfer Gap within the Gutzwiller Approximation"
Physica C 174(1991)199

R. Hayn, R. Schumann
"The Thermodynamic Density of States of the Emery model"
J. Magn. Magn. Mat. 125(1993)368

R. Schumann, M. Richter, L. Steinbeck, H. Eschrig
"Density-functional approach to the valence change in SmS: Normal and high-pressure phases"
Phys. Rev. B 52 (1995) 8801-8806

R. Schumann, A. Mishchenko, M. Richter
"Self-interaction corrected band structure of black-phase SmS"
Physica B 230-232 (1997) 516-518

R. Schumann
"Thermodynamics of a 4-site Hubbard model by analytical diagonalization"
Ann. Phys. (Leipzig) 11 (2002) 49

R. Schumann
"Analytical solution of extended Hubbard models on three- and four-site clusters"
Physica C 460-462 (2007) 1015

R. Schumann
"Analytical solution of a Hubbard model extended by nearest neighbour Coulomb and exchange interaction on a triangle and tetrahedron"
cond-mat/0701060, Ann. Phys. (Leipzig) 17 (2008) 221-259

R. Schumann, D. Zwicker
"The Hubbard model extended by nearest-neighbor Coulomb and exchange interaction on a cubic cluster - rigorous and exact results"
Ann. Phys. (Berlin) 522 (2010) 419-439


Permanent Magnets

L. Jahn, R. Schumann, V. Christoph
"The Influence of Texture on the Coercitivity of Polycristalline magnets"
phys.stat.sol.(a) 88(1985)595

L. Jahn, R. Schumann
"The Mechanism of Thermal Remagnetization of Permanent Magnets"
phys.stat.sol.(a) 91(1985)603

R. Schumann, L. Jahn
"Berechnung des Einflusses der Textur auf die Koerzitivfeldstärke polykristalliner Dauermagnete"
Elektrie Berlin 40 (1986)306

L. Jahn, K. Elk, R. Schumann
"Angular dependence of the Coercivity Force of Textured Rare Earth Magnets"
J.Magn.Magn.Mat 68(1987)161

R. Scholl, R. Schumann and L. Jahn
"The thermal remagnetization of 2:17 Sm-Co permanent magnets"
phys. stat. sol. (a) 102 (1987),K 37

L. Jahn, R. Scholl, R. Schumann
"Virgin Curves and Thermal Remagnetization of Sm2(Co,Zr,Fe,Cu)17"
Proc. 6th Intern.Sem.Magn., Dohma, 1987

K. Elk, V. Christoph, R. Schumann
"Magnetostatic Interaction in Fine Particle Magnetism"
Proc. 6th Intern.Sem.Magn., Dohma, 1987

L. Jahn, R. Schumann and P. Löwe
"Determination of the texture of high coercive hard magnets"
Proc. 6th Intern.Sem.Magn., Dohma, 1987

R. Schumann
"The Thermal Remagnetization of Permanent Magnets"
CEAM Topical Meeting on Coercicity Mechanisms, Schellerhau, April, 1992

L. Jahn, V. Christoph, D. Eckert, R. Schumannn, K.-H. Müller and R. Scholl
"Anisotropy, alignment and susceptibility of hard magnets"
Proc. Intern. Sympos. on Magn. ISPMM-92, Beijing, July 1992, 47

L. Jahn, V. Christoph, R. Schumann, S. Wirth and R. Hermann
"Influence of alignment on hard magnetic properties"
Proc. Bilateral Chinese German Symp., Beijing Juni 1992

D. Hinz, R. Schumann, K. Helming and D. Schläfer
"Texture in Hot Rolled NdFeB Ingots"
Proc. of the 13th Int. Workshop on RE Magnets & Applictions,
Birmingham (11.-14. 9. 1994), 581-590

R. Schumann
"Influence of texture on the magnetic viscosity"
J. Magn. Magn. Mat. 149 (1995) 318-330

R. Schumann, L. Jahn
"On the irreversible susceptibility of a textured Stoner-Wohlfahrt ensemble"
J. Magn. Magn. Mat. 150 (1995) 349-352

L. Jahn, R. Schumann, W. Rodewald
"Magnetic viscosity of modified neodymium iron boron magnets with high coercitivities"
J. Magn. Magn. Mat. 153 (1996) 302-310

L. Jahn, V. Ivanov, R. Schumann, and M. Loewenhaupt
"Magnetic viscosity of modified neodymium iron boron magnets with high coercitivities"
Materials Science Forum 373-376 (2001) 417

R. Schumann, L. Jahn
"Theory of thermal remagnetization of permanent magnets"
J. Magn. Magn. Mat. 232 (2001) 231

L. Jahn, R. Schumann, V. Ivanov
"Investigation of the Thermal Remagnetization in Sintered Hard Magnets"
IEEE Trans. Magn. 37 (2001) 2506

L. Jahn, V. Ivanov, R. Schumann
"Remanence Investigation and Interaction in Polycrystalline RE/T-Hard Magnets"
The Physics of Metals and Metallography 91, Suppl. 1 (2001) 268

R. Schumann, L. Jahn
"Theory of the Inverse Thermal Remagnetization in Polycrystalline Permanent Magnets"
The Physics of Metals and Metallography 91, Suppl. 1 (2001) 253

R. Schumann, P. Seidel, L. Jahn
"The Inverse Thermal Remagnetization in Barium Ferrite"
The Physics of Metals and Metallography 91, Suppl. 1 (2001) 257

L. Jahn, R. Schumann
"Field dependence of the thermal remagnetization in sintered hard magnets"
Journal of Magnetism and Magnetic Materials 251 (2002) 93

L. Jahn, V. Ivanov, R. Schumann, M. Loewenhaupt
"Influence of initial temperature on the thermal remagnetization of SmCo5 sintered magnets"
R. Schumann, L. Jahn
"Thermal remagnetization in polycristalline permanent magnets"
Recent Res. Devel. Magnetism & Magnetic Mat., 1 (2003) 383-419,
ISBN: 81-7895-100-2, cond-mat/0305292

R. Schumann, S. Kobe
"Criticality condition of the fully anisotropic Ising model with next-nearest neighbour interaction"
Physica A 386 (2007) 187-193