Magnetic phase diagram of Al-doped spinel MnV2O4

We present the structure, magnetization, and resistivity results of the spinel Al-doped MnV2O4. When small amount of Al ions substitutes V ones, the structural transition accompanying orbital order of MnV2O4 disappears. With further Al doping, the paramagnetic–ferrimagnetic transition temperature TC increased firstly and then decreased. The magnetic phase diagram is discussed in terms of the competition among the lattice shrinkage and the non-magnetic substitution aroused by Al3+ ions doping and the different degree of freedoms of lattice, spin and orbit in Mn(V1−xAlx)2O4. We also study the resistivity of these samples and find that the doping of Al ions does not change the electric transport mechanism, but increases the difficulty of electron hopping as shown in the obvious increasing of the activation energy.