Thermal Properties of Ferrimagnetic Systems

Aiman Al-Omari

.

DOI: 10.4236/wjcmp.2011.14018                

Abstract

The heat capacity of some ferrimagnets has additional structures like a shoulder in the Schottky-like peak, or emergence of a second peak when an external magnetic field is applied. It is shown here that the ferromagnetic and anti-ferromagnetic elementary excitation spectra give rise to two independent heat capacity peaks, one enveloped by the other, which add up to give the peak for the total system. Taking this into account helps understand the additional structures in the peaks. Moreover, the classification of ferrimagnets into predominantly antiferromagnetic, ferromagnetic, or a mixture of the two is shown to be validated by studying them under additional influences like dimerization and frustration. Because these two are shown to influence the ferromagnetic and antiferromagnetic dispersion rela tions—and hence the quantities like heat capacity and magnetic susceptibility—by different amounts, the characterization of ferrimagnetic systems (1,1/2), (3/2,1) and (3/2,1/2) is brought out more clearly. Both these influences enhance antiferromagnetic character. PACS numbers: 75.10.Jm, 75.50.Ge.

Keywords

Ferrimagnet, Alternat Spins, Susceptibility, Heat Capacity

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	S. Yamamoto and T. Fukui, “Thermodynamic Properties of Heisenberg Ferrimagnetic Spin Chains: Ferromag- netic-Antiferromagnetic Crossover,” Physical Review B, Vol. 57, No. 22, 1998, pp. 14008-14011. doi:10.1103/PhysRevB.57.R14008
[2]	S. Yamamoto, T. Fukui, K. Maisinger and U. Schollowo- ck, “Combination of Ferromagnetic and Antiferromag- netic Features in Heisenberg Ferrimagnets,” Journal of Physics: Condfensed Matter, Vol. 10, No. 48, 1998, p. 11033. doi:10.1088/0953-8984/10/48/023
[3]	S.-S. Gong, W. Li, Y. Zhao and G. Su, “Magnetism and Thermodynamics of Spin-(1/2, 1) Decorated Heisenberg Chain with Spin-1 Pendants,” Physical Review B, Vol. 81, No. 21, 2010, pp. 214431-214439. doi:10.1103/PhysRevB.81.214431
[4]	N. B. Ivanov, “Spin Models of Quasi-1D Quantum Ferri- magnets with Competing Interactions,” Condensed Mat- ter Physics, Vol. 12, No. 3, 2009, pp. 435-447. doi:10.5488/CMP.12.3.435
[5]	W Selke and J. Oitmaa, “Monte Carlo Study of Mixed- Spin S = (1/2, 1) Ising Ferrimagnets,” Journal of Physics: Condfensed Matter, Vol. 22, No. 7, 2010, p. 76004. doi:10.1088/0953-8984/22/7/076004
[6]	C. Wu, B. Chen, X. Dai, Y. Yu and Z.-B. Su, “Schwin- ger-Boson Mean-Field Theory of the Heisenberg Ferri- magnetic Spin Chain,” Physical Review B, Vol. 60, No. 2, 1999, pp. 1057-1063. doi:10.1103/PhysRevB.60.1057
[7]	S. K. Pati, S. Ramasesha and D. Sen, “Low-Lying Excited States and Low-Temperature Properties of an Alter- nating Spin-1-Spin-1/2 Chain: A Density-Matrix Renor- malization-Group Study,” Physical Review B, Vol. 55, No. 14, 1997, pp. 8897-8904. doi:10.1103/PhysRevB.55.8894
[8]	S. K. Pati, S. Ramasesha and D. Sen, “A Density Matrix Renormalization Group Study of Low-Energy Excitations and Low-Temperature Properties of Alternating Spin Sys- tems,” Journal of Physics: Condfensed Matter, Vol. 9, No. 41, 1997, p. 8707.
[9]	S. Yamamoto and T. Sakai, “Low-Energy Structure of Heisenberg Ferrimagnetic Spin Chains,” Journal of the Physical Society of Japan, Vol. 67, 1998, pp. 3711-3714. doi:10.1143/JPSJ.67.3711
[10]	S. Yamamoto, “Magnetic Properties of Quantum Ferrima- gnetic Spin Chains,” Physical Review B, Vol. 59, No. 2, 1999, pp. 1024-1027. doi:10.1103/PhysRevB.59.1024
[11]	S. Yamamoto, T. Fukui and T. Sakai, “Characterization of Ferrimagnetic Heisenberg Chains According to the Cons- tituent Spins,” cond-mat/0001004 (2000).
[12]	S. Yamamoto, “Modified Spin-Wave Description of the Nu- clear Spin Relaxation in Ferrimagnetic Heisenberg Chains,” cond-mat/ 0004297 (2000).
[13]	K. Maisinger, U. Schollw?ck, S. Brehmer, H.-J. Mikeska, and S. Yamamoto, “Thermodynamics of the (1, 1/2) Fer- rimagnet in Finite Magnetic Fields,” Physical Review B, Vol. 58, No. 10, 1998, pp. 5908-5911. doi:10.1103/PhysRevB.58.R5908
[14]	A. Al-Omari and A. H. Nayyar, “The Combined Effect of Frustration and Dimerization in Ferrimagnetic Chains and Square Lattices,” Journal of Physics: Condfensed Matter, Vol. 12, No. 48, 2000, p. 1194. doi:10.1088/0953-8984/12/48/311
[15]	S. Brehmer, H. -J. Mikeska and S. Yamamoto, “Low-Tem- perature Properties of Quantum Antiferromagnetic Chains with Alternating Spins S = 1 and S = 1/2,” Journal of Physics: Condfensed Matter, Vol. 9, No. 19, 1997, p. 3921. doi:10.1088/0953-8984/9/19/012
[16]	S. Yamamoto, S. Brehmer and H.-J. Mikeska, “Elementa- ry Excitations of Heisenberg Ferrimagnetic Spin Chains,” Physical Review B, Vol. 57, No. 21, 1998, p. 13610.
[17]	N. Ivanov, J. Richter and U. Schollwock, “Frustrated Quan- tum Heisenberg Ferrimagnetic Chains,” Physical Review B, Vol. 58, No. 21, 1998, pp. 14456-14461. doi:10.1103/PhysRevB.58.14456
[18]	N. Ivanov, “Spin-Wave Series for Quantum One-Dimen- sional Ferrimagnets,” Physical Review B, Vol. 57, No. 22, 1998, p. 14024.
[19]	A. Al-Omari, “Self-Consistent Approximation for Dime- rization of Ferrimagnets on Chains and Square Lattices,” Physical Review B, Vol. 59, No. 14, 1999, pp. 9304-9313. doi:10.1103/PhysRevB.59.9304
[20]	T. Sarkar, V. Pralong, V. Caignaert and B. Raveau, “Com- petition between Ferrimagnetism and Magnetic Frustration in Zinc Substituted YBaFe4O7,” Chemistry of Materials, Vol. 22, No. 9, 2010, p. 2885.
[21]	A. Winkler, N. Narayanan, D. Mikhailova, K. G. Bramnik, H. Ehrenberg, H. Fuess, G. Vaitheeswaran, V. Kanchana, F. Wilhelm, A. Rogalev, A. Kolchinskaya and L. Alff, “Magnetism in Re-Based Ferrimagnetic Double Pero- vskites,” New Journal of Physics, Vol. 11, No. 7, 2009, p. 73047. doi:10.1088/1367-2630/11/7/073047
[22]	A. Al-Omari and A. H. Nayyar, “Dimerization of Ferrimagnets on Chains and Square Lattices,” Journal of Physics: Condfensed Matter, Vol. 11, No. 2, 1999, p. 465. doi:10.1088/0953-8984/11/2/012