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Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Magnetism is the study of magnetic phenomena and their laws. Magnetism arises from the spinning motion of electrons so that each electron produces a small magnetic field. The magnetic effects of electrons spinning in opposite directions cancel each other out. Magnetism is of four types: diamagnetism, paramagnetism, ferromagnetism, and ferrimagnetism. In diamagnetism, the magnetization is opposite to the applied magnetic field, weak and temporary. Diamagnetic materials contain paired electrons. In paramagnetism, it is in the same direction as the applied magnetic field, but weak and temporary. In ferromagnetism occurring in materials like iron, cobalt, and nickel, there is an enormous increase in magnetization in the same direction as the field, due to the alignment of regions of aligned electron spin called domains. Moreover, magnetism is retained even after removal of the field. Both paramagnetic and ferromagnetic materials contain unpaired electrons. Antiferromagnetism is a property possessed by some metals, alloys, and salts of transition elements, such as manganese oxide (MnO), by which the atomic magnetic moments form an ordered array that alternates or spirals, so as to give no net total moment in zero applied magnetic field and hence almost no gross external magnetism. In ferrimagnetism, which is observed in composite materials, such as magnetite, rather than individual elements, the overall spin effect in one direction is greater than that in the other.
Living in a Magnetic World
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
French physicist Louis Felix Néel (1904–2000) suggested the existence of antiferromagnetism around 1930, and that above a certain temperature—which has now taken his name—antiferromagnetic materials cease to show the ordered arrangement of their magnetic moments, and hence the antiferromagnetism stops. Most antiferromagnetic materials are ionic compounds like MnO, and include FeO and NiO.
Crystals and Glasses
Published in Marvin J. Weber, and TECHNOLOGY, 2020
Merritt N. Deeter, Gordon W. Day, Allen H. Rose
In ferromagnetic materials, the spins of unpaired electrons spontaneously align parallel to each other. This arrangement produces a net magnetic moment which is generally largest at low temperatures, decreases monotonically with increasing temperature, and eventually vanishes at the Curie temperature Tc. In antiferromagnetic materials, nearest neighbor spins align in an antiparallel arrangement such that their magnetic moments tend to cancel. A subclass of antiferromagnetic materials is the canted antiferromagnets in which nearest neighbor spins are not quite antiparallel and thus add vectorially to result in a small magnetic moment. Finally, ferrimagnetic systems consist of two or more spatially superimposed magnetic “sublattices” which couple antiferromagnetically but generally differ in magnetization and thus produce a finite magnetic moment.
Magnetism in an antiferromagnetic Ising nano-ladder under an applied transverse field
Published in Phase Transitions, 2019
The research of low-dimensional quantum antiferromagnets has a long history and has exhibited a rich variety of characteristic phenomena, such as the ground state and excited state phenomena. The spin ladder antiferromagnetic systems are also another interesting research subjects experimentally and theoretically. Theoretically, they are usually described by the Heisenberg ladder models, which are quantum problems and could not be solved exactly. On the other hand, recent developments of experimental techniques have exhibited a lot of novel information for low-dimensional antiferromagnetic nano-systems, namely nano-chains and nano-ladders [1,2]. In particular, the authors in [1] have argued that the antiferromagnetic nano-systems exhibit the stable Neel state and they may be well described by the Ising model. These nanoscaled antiferromagnets have been proposed as useful candidates for future technological applications. As far as we know, an antiferromagnetic nanoscaled ladder system described by the transverse Ising model (TIM) has not been investigated.
Transition metal salts of quinoline: synthesis, structure and magnetic behavior of (QuinH)2[MX4]·2H2O [Quin = quinoline; M = Mn, Co, Cu, Zn], (QuinH)2[MnBr2(H2O)2](Br)2 and (QuinH)[Cu(Quin)Br3]
Published in Journal of Coordination Chemistry, 2018
Christopher P. Landee, Jeffrey C. Monroe, Robert Kotarba, Matthew Polson, Jan L. Wikaira, Mark M. Turnbull
All the magnetic interactions in the compounds studied were antiferromagnetic. For that reason, the Hamiltonian used for the following analyses has the form with a positive J corresponding to antiferromagnetic interactions and the singlet-triplet gap equal to 2J. Magnetic exchange is proposed to occur via the two-halide pathway [27] for 1, 2, 4, 6 and 7. The distance and angle parameters for the contacts are provided in Table 4.