Studying the interaction between light and matter is a fundamental and powerful approach for physicists to probe the microcosmic world. Recent advancements in ultrafast optics, particularly the development of femtosecond laser pulses, have enabled the study of these interactions on unprecedented timescales. This has propelled research into ultrafast spin dynamics within magnetic materials, a central focus in modern condensed matter physics with direct implications for the advancement of spintronic technologies. This review provides a comprehensive discussion of ultrafast electron relaxation dynamics in magnetic materials as investigated via femtosecond laser pump-probe spectroscopy. This powerful technique serves as the primary methodological foundation for the discussed research, allowing for direct temporal observation of non-equilibrium states following laser excitation. We synthesize and examine the substantial body of related international and domestic research progress, detailing the characteristic timescales and pathways of energy dissipation following optical excitation. Furthermore, the review critically assesses the various proposed microscopic mechanisms that seek to explain these ultrafast processes, including models involving electron–electron scattering, electron–phonon coupling, and spin–lattice interactions. By consolidating empirical findings with theoretical frameworks, this work aims to clarify the current understanding of the fundamental processes governing ultrafast demagnetization and subsequent relaxation. The critical discussion presented herein not only consolidate the current understanding of ultrafast electron relaxation in laser-excited magnetic materials but also provide valuable insights and guidance for future investigations in this rapidly evolving field, which is of great significance for promoting the practical application of spintronic devices and advancing the frontier of condensed matter physics research.

This paper presents an extensive experimental and theoretical investigation of the cesium-doped methylammonium lead triiodide (Cs: MAPbI₃), a hybrid inorganic-organic perovskite that exhibits high photovoltaic and nonlinear optical (NLO) promise. The reaction mechanism at the molecular level suggests coordination of the Pb²⁺ with the iodide ions and Cs⁺-induced zwitterionic nature, which favors exciton dissociation and charge separation. Crystallographic analysis reveals favored crystallization in the (101) plane and reveals a three-dimensional intricate system of molecular slabs, tubular morphologies, helical molecular strips, and sloping planes, all for anisotropic charge transfer. The pseudo-tetragonal lattice exhibits low Microstrain (ε = 3.49 × 10⁻⁴), high crystallite dimension (812.2 nm), and high phase purity, as established by XRD and SEM studies. Electrochemical impedance spectroscopy gives low series resistance (Rs = 15.2 Ω) and high recombination resistance (Rrec = 600 Ω), suggestive of optimal carrier transport. Band gap value optimized to ~ 1.55–1.63 eV is comparable with the Shockley–Queisser limit, and the material has a high external quantum efficiency (EQE ~ 86%). Spectroscopic analyses (FT-IR, FT-Raman, NMR) authenticate polar strong interactions (e.g., Pb-I, Pb-H, Cs-I), which are responsible for vibrational coupling and dielectric modulation. Theoretical calculations, such as APT, Mulliken population, HOMO-LUMO analysis, UV-Vis absorption, and NBO analysis, indicate extensive delocalization of electrons, strong orbital hybridization, and favourable dipole alignment, along with highly developed hyperpolarizability (βtot = 528.19 × 10⁻³³ esu) to facilitate intense second-order NLO activity. MEP map and exciton cavity analysis emphasize dipolar energy landscapes conducive to exciton confinement and dissociation. Collectively, these photophysics, electronics, and structure result in Cs: MAPbI₃ as a structurally stable, optically active, and electronically tuneable material that is best suited for high-performance applications in solar energy and nonlinear photonics.

Abstract Magnetic Resonance Imaging (MRI) is a very powerful tool for cancer diagnosis today. At present, however, there is still a lot of confusion about how this technology was developed and who were the major discoverers in this field. Particularly, there was a strong dispute between the followers of two scientists, R. Damadian and P. Lauterbur. Also, it was not clear about the physical mechanism that allows NMR to be used to detect cancer. In this review, we carefully trace the major developments in using NMR for cancer detection starting from day one, that was almost 50 years ago. One can see from the research records that the truth was beyond the claims of the popular science literatures. The development of NMR for cancer detection involved several research groups, who made important contributions at different stages. Particularly, the key discovery leading to the development of MRI was the finding that the relaxation times and spin diffusion coefficient of water protons changed when cells became tumor. The physical mechanisms responsible for these changes are discussed in this review.

Welcome to Discover Physics, a fully open access journal within the Discover series, covering all aspects of research in physics.By nature, humans have always been curious about the world we live in.This curiosity to understand the nature of our universe has, for centuries, driven scientific advancement and built the branch of science that we call physics.Advancements in physics have increased our understanding of the behavior of nature, from the discovery of the cosmic microwave background [1] to the generation of attosecond light pulses [2].Discoveries in physics have also directly impacted our everyday lives in the twentieth and twenty-first centuries, from Wilhem Rntgen's discovery of X-rays, for which he was awarded the first Nobel Prize in Physics in 1901 [3], to the development of machine learning, for which John Hopfield and Geoffrey Hinton were awarded the same prize in 2024 [4].Discover Physics was established to be a home for advancements in physics from all research areas.