A novel soft magnetic composite with ultrastable permeability up to gigahertz frequencies has been developed through cold sintering of ultrafine FeSiAl particles, magnetically isolated and covalently bonded by a multilayered heterostructure of Al₂SiO₅/SiO₂/Fe₂(MoO₄)₃. This composite exhibits a permeability of 13 up to 1 GHz, a saturation magnetization of 105 Am²/kg, and a low coercivity of 48 A/m, attributed to the elimination of domain walls in single-vortex structures. The composite also demonstrates a high ultimate compressive strength of 337.1 MPa due to epitaxially grown interfaces. The magnetic vortex structure, observed via Lorentz transmission electron microscopy and micromagnetic simulations, provides a stable permeability and enhances magnetic performance. The composite outperforms traditional materials in high-frequency applications, with a PCB-embedded inductor showing stable inductance and high quality factor. The study highlights the potential of magnetic vortices in high-frequency magnetic devices and provides insights into the design of integrated magnetic components. The cold sintering process enables the formation of a multilayered heterostructure, enhancing mechanical strength and magnetic properties. The results demonstrate the effectiveness of magnetic isolation in achieving frequency-stable permeability and offer a new approach for developing high-performance magnetic materials.A novel soft magnetic composite with ultrastable permeability up to gigahertz frequencies has been developed through cold sintering of ultrafine FeSiAl particles, magnetically isolated and covalently bonded by a multilayered heterostructure of Al₂SiO₅/SiO₂/Fe₂(MoO₄)₃. This composite exhibits a permeability of 13 up to 1 GHz, a saturation magnetization of 105 Am²/kg, and a low coercivity of 48 A/m, attributed to the elimination of domain walls in single-vortex structures. The composite also demonstrates a high ultimate compressive strength of 337.1 MPa due to epitaxially grown interfaces. The magnetic vortex structure, observed via Lorentz transmission electron microscopy and micromagnetic simulations, provides a stable permeability and enhances magnetic performance. The composite outperforms traditional materials in high-frequency applications, with a PCB-embedded inductor showing stable inductance and high quality factor. The study highlights the potential of magnetic vortices in high-frequency magnetic devices and provides insights into the design of integrated magnetic components. The cold sintering process enables the formation of a multilayered heterostructure, enhancing mechanical strength and magnetic properties. The results demonstrate the effectiveness of magnetic isolation in achieving frequency-stable permeability and offer a new approach for developing high-performance magnetic materials.