Gravity is actually stronger at the Earth's inner core compared to the outer core. The inner core is the solid innermost layer of the Earth, while the outer core is a liquid layer surrounding the inner core. The variation in gravity between the two regions is primarily due to differences in density and mass distribution.
Gravity is directly proportional to the mass of an object. The inner core, despite being smaller in size, has a higher density and mass compared to the outer core. The higher density is a result of the immense pressure at the Earth's core, which compresses the materials and increases their density.
The gravitational force experienced at any point within the Earth depends on the mass contained within the sphere with that point at its center. Since the inner core has a higher mass concentration compared to the outer core, the gravitational force is stronger in the vicinity of the inner core.
It is worth noting that the density and mass distribution within the Earth's core are still subjects of ongoing scientific research, and our understanding of these regions is based on seismic data, modeling, and indirect observations. Nevertheless, based on our current knowledge, gravity is generally expected to be stronger towards the center of the Earth, including the inner core.