The article discusses the magnetic properties of nanoparticles, particularly focusing on surface effects and their applications in biomedicine, with a specific emphasis on ferrite nanoparticles and their use as contrast agents in magnetic resonance imaging (MRI). Magnetic nanoparticles exhibit unique properties due to their finite size, high surface-to-volume ratio, and different crystal structures compared to bulk materials. These properties make them suitable for various biomedical applications, including MRI. The surface effects, such as surface defects, oxidation, and strain, can significantly influence the magnetic behavior of nanoparticles, leading to phenomena like ferromagnetism, antiferromagnetism, and superparamagnetism. The article also explores the core-shell interactions in ferrite nanoparticles, where the exchange coupling between the core and shell can affect magnetic properties like coercivity and remanence. The magnetic properties of ferrite nanoparticles, such as permeability, coercivity, and saturation magnetization, can be tuned by controlling synthesis methods and particle size, making them valuable for technological applications. The study of these properties is crucial for understanding and optimizing the performance of magnetic nanoparticles in biomedical applications.The article discusses the magnetic properties of nanoparticles, particularly focusing on surface effects and their applications in biomedicine, with a specific emphasis on ferrite nanoparticles and their use as contrast agents in magnetic resonance imaging (MRI). Magnetic nanoparticles exhibit unique properties due to their finite size, high surface-to-volume ratio, and different crystal structures compared to bulk materials. These properties make them suitable for various biomedical applications, including MRI. The surface effects, such as surface defects, oxidation, and strain, can significantly influence the magnetic behavior of nanoparticles, leading to phenomena like ferromagnetism, antiferromagnetism, and superparamagnetism. The article also explores the core-shell interactions in ferrite nanoparticles, where the exchange coupling between the core and shell can affect magnetic properties like coercivity and remanence. The magnetic properties of ferrite nanoparticles, such as permeability, coercivity, and saturation magnetization, can be tuned by controlling synthesis methods and particle size, making them valuable for technological applications. The study of these properties is crucial for understanding and optimizing the performance of magnetic nanoparticles in biomedical applications.