Inner core is solid and outer core is liquid even though temperature of inner core is higher than outer temperature.
It is because state of the body does not depend upon only temperature but also in pressure and melting point of materials.
Explanation:
Inner part of earth is called core. It has two parts outer core which has nickel-iron alloy and has radius 2100 km (according to NASA) inner core which has iron as the main element which has radius around 1220 km (according to NASA).
Pressure of inner core is higher than outer core and as pressure increases the melting point of iron in inner core also increases.
