In quantum mechanics, magnetic resonance is a resonant effect that can appear when a magnetic dipole is exposed to a static magnetic field and perturbed with another, oscillating electromagnetic field. Due to the static field, the dipole can assume a number of discrete energy eigenstates, depending on the value of its angular momentum (azimuthal) quantum number. The oscillating field can then make the dipole transit between its energy states with a certain probability and at a certain rate. The overall transition probability will depend on the field's frequency and the rate will depend on its amplitude. When the frequency of that field leads to the maximum possible transition probability between two states, a magnetic resonance has been achieved. In that case, the energy of the photons composing the oscillating field matches the energy difference between said states. If the dipole is tickled with a field oscillating far from resonance, it is unlikely to transition. That is analogous to other resonant effects, such as with the forced harmonic oscillator. The periodic transition between the different states is called Rabi cycle and the rate at which that happens is called Rabi frequency. The Rabi frequency should not be confused with the field's own frequency. Since many atomic nuclei species can behave as a magnetic dipole, this resonance technique is the basis of nuclear magnetic resonance, including nuclear magnetic resonance imaging and nuclear magnetic resonance spectroscopy.
The phenomenon of magnetic resonance is rooted in the existence of spin angular momentum of a quantum system and its specific orientation with respect to an applied magnetic field. Both cases have no explanation in the classical approach and can be understood only by using quantum mechanics. Some people claim[who?] that purely quantum phenomena are those that cannot be explained by the classical approach. For example, phenomena in the microscopic domain that can to some extent be described by classical analogy are not really quantum phenomena. Since the basic elements of magnetic resonance have no classical origin, although analogy can be made with Classical Larmor precession, MR should be treated as a quantum phenomenon.
GQDs/Co0.5Zn0.5Fe2O4 nanocomposite was synthesized using a facile sonication-assisted approach. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental dispersive X-ray spectroscopy (EDX), impedance analyzer and vibrating sample magnetometer (VSM) were employed to characterize the synthesized samples. The XRD data confirmed the formation of GQDs, Co-Zn ferrite and GQDs/Co-Zn ferrite nanocomposite with no detectable impurity peaks. FTIR results identified the presence of GQDs in GQDs/Co-Zn ferrite nanocomposite. The morphological study revealed the decoration of spherical GQDs on the surface of Co-Zn ferrite. Complex impedance plane plots showed the contribution of the relaxation phenomenon associated with grain and grain boundaries in observed dielectric properties of the nanocomposite. The inclusion of GQDs led to the enhancement of the dielectric constant of the nanocomposite at low frequencies. GQDs/Co0.5Zn0.5Fe2O4 showed superparamagnetic properties which makes it a potential material to be used as a contrast agent in magnetic resonance imaging (MRI) applications.
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