Magnetic properties of the Fe₃O₄-based frozen ferrofluids (FFF) are investigated using a neutron depolarization (ND) technique at the temperature range from 20 to 290K and at the magnetic field from 80 to 8000A/m. The investigated FFFs (1, 2, 3) with concentration about 10% differ in an average diameter of the particle (51, 53, 67 Å). with dispersion (0.20, 0.53, 0.51), respectively. It was found that the ferrofluids frozen in zero magnetic field can build magnetic dipole glasses with spin-glass-like behavior, e.g. with a long-time relaxation of the magnetization and irreversibility at low temperature. The data can be interpreted in terms of an energy balance of magnetic (dipole interactions, magnetic field) and thermal contributions.