This paper presents a general theory of spin fluctuations and thermodynamic properties of itinerant electron magnets, interpolating between the weak and strong ferromagnetic limits. The authors discuss the Curie temperature and the physical meaning of the Curie-Weiss magnetic susceptibility. They also explore new phenomena arising from this theory, such as temperature-dependent local magnetic moments observed in CoS₂, CoSe₂, and the magnetic and thermal properties of nearly ferromagnetic semiconductors like FeSi. The theory is based on a Hubbard-type Hamiltonian with intra-atomic electron-electron interactions and considers spin and charge density fluctuations. The self-consistent renormalization (SCR) theory of spin fluctuations is used to explain the Curie-Weiss susceptibility and other physical properties. The authors show that the local moment picture is a limiting form of more general spin density fluctuations. The paper discusses the Curie temperature and magnetic susceptibility, showing that the Curie-Weiss law is best satisfied in the two opposite limits of the theory. The authors also analyze the temperature-induced local magnetic moments in Co(SₓSe₁₋ₓ)₂, where the susceptibility changes from a Curie-Weiss type to a local moment type at a certain temperature. They also discuss the magnetic and thermal properties of nearly ferromagnetic semiconductors like FeSi, showing that the theory can explain these properties. The paper concludes that the theory provides a unified description of itinerant electron ferromagnetism, interpolating between the local moment and weak ferromagnetic limits. It also shows that spin fluctuations are important in both limits and that the longitudinal spin fluctuations are particularly important in the weak ferromagnetic limit. The authors suggest that the theory can be used to explain the magnetic and thermal properties of various materials, including nearly ferromagnetic semiconductors and magnetic insulators.This paper presents a general theory of spin fluctuations and thermodynamic properties of itinerant electron magnets, interpolating between the weak and strong ferromagnetic limits. The authors discuss the Curie temperature and the physical meaning of the Curie-Weiss magnetic susceptibility. They also explore new phenomena arising from this theory, such as temperature-dependent local magnetic moments observed in CoS₂, CoSe₂, and the magnetic and thermal properties of nearly ferromagnetic semiconductors like FeSi. The theory is based on a Hubbard-type Hamiltonian with intra-atomic electron-electron interactions and considers spin and charge density fluctuations. The self-consistent renormalization (SCR) theory of spin fluctuations is used to explain the Curie-Weiss susceptibility and other physical properties. The authors show that the local moment picture is a limiting form of more general spin density fluctuations. The paper discusses the Curie temperature and magnetic susceptibility, showing that the Curie-Weiss law is best satisfied in the two opposite limits of the theory. The authors also analyze the temperature-induced local magnetic moments in Co(SₓSe₁₋ₓ)₂, where the susceptibility changes from a Curie-Weiss type to a local moment type at a certain temperature. They also discuss the magnetic and thermal properties of nearly ferromagnetic semiconductors like FeSi, showing that the theory can explain these properties. The paper concludes that the theory provides a unified description of itinerant electron ferromagnetism, interpolating between the local moment and weak ferromagnetic limits. It also shows that spin fluctuations are important in both limits and that the longitudinal spin fluctuations are particularly important in the weak ferromagnetic limit. The authors suggest that the theory can be used to explain the magnetic and thermal properties of various materials, including nearly ferromagnetic semiconductors and magnetic insulators.