Trivalent Al3+-doped samples of magnetite (Alx ${\mathrm {Fe}}_{3-x}\text{O}$ 4, $0.01\le x \le1.0$ ) were produced by wet chemical method. The X-ray diffraction studies confirmed the formation of a single-phase inverse spinel-type structure. Particles having spherical morphology and size range lying between 4 and 25 nm were observed during transmission electron microscopic investigation. Magnetic measurement displayed increase in saturation magnetization with a maximum value of ~62 $\text{A}\cdot \text{m}$ 2/kg for $x =0.1$ , and thereafter, it started decreasing with increased concentration of Al. The temperature during magnetic hyperthermia got stabilized near therapeutic range (~315 K) for the samples such as $x =0.01$ , 0.5, 0.7, and 1.0 at various external alternating current magnetic fields.