Combined effect of 2D nature and structural glass behaviour and true magnetic contribution to the low-temperature heat capacity of layered double hydroxides

Heat capacity of cobalt-aluminium and magnesium-aluminium layered double hydroxides (LDH) with the divalent-to-trivalent cations ratio ( n ) of 2 and 3, and intercalated with NO 3 − , CO 3 2− and OH − , was measured as a function of temperature between 2 and 100 K. Magnetic contribution to the heat capacity ( C mag ) of Co n Al LDH was extracted from comparison of the C ( T ) dependences with the respective reduced dependences of their non-magnetic counterparts, Mg n Al LDH. At the lowest measured temperatures, the magnetic contribution to the heat capacity ( C mag ) of Co-containing LDH was found to be almost two orders of magnitude bigger than their lattice contribution. In a zero magnetic field, the low-temperature C mag of Co 2 Al LDH was measured to be proportional to T 2.6 , while for Co 3 Al LDH, C mag ∼ T 2 was observed. An application of an external magnetic field was revealed to converge these dependences to C mag ∼ T 3 in compounds with both n = 2 and 3. However, the conversion in Co 2 Al LDH occurred at lower values of external magnetic field (50 kOe) than that in Co 3 Al LDH (90 kOe). It was revealed from the C ( T ) behaviour of the non-magnetic LDH at the lowest measured temperatures that they possess the features typical for both a 2D solid and a structural glass. The reduced C ( T )/ T 3 heat capacity of Mg n Al LDH intercalated with nitrate was found to demonstrate a so-called boson peak, which is a manifestation of a glassy state. The observed low-temperature structural glassy state in LDH was associated with the disorder of the intercalated species. • Magnetic contribution ( C mag ) is the dominant contribution to the heat capacity of Co Al LDH at low T . • Low- T heat capacity of LDH demonstrates the features typical for both a 2D solid and a structural glass. • Boson peak in the lattice heat capacity versus T is an indicator of the interlayer disorder in LDH. • Extracted magnetic contribution to C ( T ) reflects intrinsic differences in magnetic nature of LDH.