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Investigations of the heterometallic Ludwigite Ni${_2}$AlBO${_5}$

We present magnetic, thermodynamic, dielectric and structural investigations on the aluminoborate Ni${_2}$AlBO${_5}$, belonging to the ludwigite family. Room temperature structural refinement suggests that the system crystallizes in the orthorhombic $Pbam$ symmetry, in similarity with most members of this material class. Magnetic and thermodynamic measurements shows that the system undergoes a phase transition to an antiferromagnetic state at 38K, signatures of which are also seen in the lattice parameters and the dielectric constant. Short range magnetic correlations appear to persist to much higher temperatures - a regime in which the ac susceptibility exhibits a power law temperature dependence, in agreement with that expected for random exchange Heisenberg antiferromagnetic spin chains.