Magnetic **** vibration refers to the phenomenon of spin magnetic resonance. It has a broader meaning, encompassing nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), or electron spin resonance (ESR).
In addition, people in their daily lives often say magnetic **** vibration, refers to the magnetic **** vibration imaging (Magnetic Resonance Imaging, MRI), which is the use of nuclear magnetic **** vibration phenomenon made of a class of imaging equipment used for medical examinations.
Magnetic **** vibration (except cyclotron **** vibration) is classically described as follows: atoms, electrons, and nuclei have angular momentum, and the ratio of their magnetic moments to the corresponding angular momentum is called the magnetic spin ratio γ. The magnetic moment M is subjected to a torque MBsinθ (θ is the angle between M and B) in a magnetic field B. This torque causes the magnetic moment to travel around the magnetic field B. The magnetic moment is then subjected to a torque θ (θ is the angle between M and B), which causes the magnetic moment to travel around the field. This torque causes the magnetic moment to move around the magnetic field in a progressive motion, and the angular frequency of the progressive motion ω = γB,ωo is called the Larmor frequency. Due to the damping effect, this incoming motion will decay away quickly, i.e., M reaches parallel to B and the incoming motion stops. However, if a high-frequency magnetic field b(ω) (angular frequency ω) is added to the perpendicular direction of the magnetic field B, the torque generated by the action of b(ω) causes M to leave B, contrary to the action of damping. If the angular frequency of the high-frequency magnetic field is equal to the Larmor (angular) frequency of the magnetic moment advance ω = ωo,then the action of b (ω) is the strongest, and the angle of advance of the magnetic moment M (the angle between M and the angle of B) is also the largest. This phenomenon is known as magnetic **** vibration.
Magnetic **** vibration can also be described by quantum mechanics: constant magnetic field B so that the magnetic spin system of the ground state energy level cleavage, cleavage of the energy level known as the Seeman energy level (see the Seeman effect), when the spin quantum number S = 1/2, the cleavage distance of the 墹 E = g μBB, g for the Lund factor, μ for the Bohr magneton, e and me for the charge and mass of the electron. When a high-frequency magnetic field b(ω) is applied perpendicular to B, the light quantum energy is 啚ω. If it is equal to the Cermann energy level cleavage spacing, 啚ω = gμBB = 啚γB, i.e., ω = γB (啚 = h/2π, with h being the Planck's constant), then the spin system will absorb this energy and jump from the low-energy state to the high-energy state (the excited state), which is known as the ****vibrational jump between the magnetic Cermann energy levels. The quantum description of the magnetic *** vibration condition, ω = γB, is the same as the result of the image-only description.
When M is the magnetic moment of an atom (ion) in a paramagnet, this magnetic **** vibration is a paramagnetic **** vibration. When M is the magnetization strength (magnetic moment per unit volume) in a ferromagnet, this magnetic **** vibration is a ferromagnetic **** vibration. When M=Mi is the magnetization strength of the ith magnetic sublattice in a subferromagnet or antiferromagnet, this magnetic **** vibration is a subferromagnetic **** vibration or antiferromagnetic **** vibration generated by a system of i coupled magnetic sublattices. When M is a nuclear magnetic moment in matter, it is a nuclear magnetic **** vibration. These kinds of magnetic **** oscillations are generated by spin magnetic moments and can be described uniformly by the classical image-only spin equation dM/dt = γMBsinθ [the corresponding vector equation is d M/dt = γ( M × B].
Gyrating *** vibration phenomenon produced by charged particles in a constant magnetic field. Let the charged particle with charge q and mass m move in a constant magnetic field B, with a speed v. When the magnetic field B is mutually perpendicular to the speed v, the charged particle is subject to the Lorentz force generated by the magnetic field, causing the charged particle to rotate with a speed v around the magnetic field B, and the angular frequency of the rotation is called the cyclotron angular frequency. If a high-frequency electric field E (ω) (ω is the angular frequency of the electric field) is added in the plane perpendicular to B, and ω = ωc, then this charged particle will be periodically accelerated by the electric field E (ω). Because this is similar to the role of the cyclotron, it is called cyclotron **** vibration. It is also called antimagnetic **** vibration because it is similar to antimagnetism when no high-frequency electric field is added. When v is perpendicular to B, the equation describing the motion of this **** vibration is d (mv) / dt = q (vB), if the quantum mechanical image description, the cyclotron **** vibration can be regarded as a high-frequency electric field induced by the state of motion of the charged particles in the magnetic field produced by the Landau energy level of the jump, to meet the conditions of the *** vibration of the jump is:
Magnetic **** vibration
ω = ωc.
Between the equilibrium state of various solid magnetic **** vibrations under the action of a constant magnetic field and the equilibrium state under the simultaneous action of a constant magnetic field and a high-frequency magnetic field (a high-frequency electric field in the case of cyclotron **** vibrations), there generally exists a process of transfer and redistribution of energy within the solid internal spin (magnetic moment) system (a current-carrying system in the case of cyclotron **** vibrations) itself and between itself and its system of dots, which is called the magnetic **** vibration relaxation process, referred to as magnetic relaxation. In the case of spin magnetic **** vibration, magnetic relaxation consists of spin-spin (S-S) relaxation within the spin (magnetic moment) system and spin-dot (S-L) relaxation between the spin system and the dot system. The time taken for the relaxation process from one equilibrium state to another is called the relaxation time, which is a measure of the rate of energy transfer or loss. The *** vibration linewidth represents the energy level width and the relaxation time represents the lifetime of that energy state. The magnetic *** vibration linewidth is closely related to the magnetic relaxation process (time), and according to the principle of immeasurability, the product of the energy level widths and the lifetime of the energy state is a constant, i.e., the *** vibration linewidth is inversely proportional to the relaxation time (the rate of energy transfer). Therefore, magnetic *** vibration is an important method to study the magnetic relaxation process and magnetic loss mechanism.
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