In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

The key methods for the preparation of magnetic nanoparticles are described systematically. The experimental data on their properties are analysed and generalised. The main theoretical views on the magnetism of nanoparticles are considered.

https://iopscience.iop.org/article/10.1070/RC2005v074n06ABEH000897/pdf

Magnetic nanoparticles: preparation, structure and properties

Preface. Contents of volumes 1-6. 1. Magnetism in ultrathin transition metal films (U. Gradmann). 2. Energy band theory of metallic magnetism in the elements (V.L. Moruzzi, P.M. Marcus). 3. Density functional theory of the ground state magnetic properties of rare earths and actinides (M.S.S. Brooks, B. Johansson). 4. Diluted magnetic semiconductors (J. Kossut, W. Dobrowolski). 5. Magnetic properties of binary rare-earth 3d-transition-metal intermetallic compounds (J.J.M. Franse, R.J. Radwanski). 6. Neutron scattering on heavy fermion and valence fluctuation 4f-systems (M. Loewenhaupt, K.H. Fischer). Author index. Subject index. Materials index.

Handbook of Magnetic Materials

Ferromagnetism usually only occurs in materials containing elements that form covalent 3d and 4f bonds. Its occurrence in pure carbon is therefore surprising, even controversial. A systematic magnetic force microscope study indicates that ferromagnetism in graphite is the result of localized spins that arise at grain boundaries.

/pdf/room-temperature-ferromagnetism-in-graphite-driven-by-two-36ae7e3kaz.pdf

Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects

Debjani Karmakar,1 S. K. Mandal,2 R. M. Kadam,3 P. L. Paulose,4 A. K. Rajarajan,5 T. K. Nath,2 A. K. Das,2 I. Dasgupta,6 and G. P. Das7 1Technical Physics & Prototype Engineering Division, Bhabha Atomic Research Center, Mumbai 400085, India 2Department of Physics & Meteorology, Indian Institute of Technology, Kharagpur 721302, India 3Radiochemistry Division, Bhabha Atomic Research Center, Mumbai 400085, India 4Tata Institute of Fundamental Research, Mumbai 400005, India 5Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400085, India 6Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076, India 7Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700032, India Received 18 August 2006; revised manuscript received 7 December 2006; published 2 April 2007

Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory

Electric field controlled magnetic exchange bias and magnetic state switching at room temperature in Ga-doped α-Fe2O3 oxide

Study of low temperature ferromagnetism, surface paramagnetism and exchange bias effect in α-Fe1.4Ga0.6O3 oxide

Doping of Ga in antiferromagnetic semiconductor α-Cr 2 O 3 and its effects on magnetic and electronic properties

Role of interfacial disorder on room temperature ferromagnetism and giant dielectric constant in nano-sized Co1.5Fe1.5O4 ferrite grains

Magnetic properties of mechanical alloyed α-Fe1.4Ti0.6O3 were studied at broad scale of temperatures, starting from room temperature down to 5 K. Morin transition of the base compound α-Fe2O3 was not observed after Ti doping. Enhanced ferromagnetism and exchange bias effect were exhibited in the alloyed compound α-Fe1.4Ti0.6O3. The observations were examined from different aspects of the alloying process, e.g., magnetic solution (spin ordering) at the interfaces of rhombohedral planes and core-shell structure of the nano-grains. Interfacial magnetic modifications were seen to be affected by the factors associated with grain size variation during alloy formation and thermal annealing of the alloy. Detailed analyses were made to understand the surface magnetism and exchange bias effect in the samples. Magnetic features of the present samples in many cases were found to be unconventional in comparison with the simple grain size effect of magnetic particles.

R.N. Bhowmik

Papers

Electric field controlled magnetic exchange bias and magnetic state switching at room temperature in Ga-doped α-Fe2O3 oxide

Study of low temperature ferromagnetism, surface paramagnetism and exchange bias effect in α-Fe1.4Ga0.6O3 oxide

Doping of Ga in antiferromagnetic semiconductor α-Cr 2 O 3 and its effects on magnetic and electronic properties

Role of interfacial disorder on room temperature ferromagnetism and giant dielectric constant in nano-sized Co1.5Fe1.5O4 ferrite grains

Study of surface magnetism, exchange bias effect, and enhanced ferromagnetism in α-Fe1.4Ti0.6O3 alloy