The investigation of material candidates with well-defined spin polarisation at room temperature is of significant interest to the developing research in the field of Spintronics.

The class of materials, known as Heusler alloys, have gained attention due to their predicted half-metallic behaviour that results in an electronic band structure where electrons can be up to 100% spin polarised. Preserving the half-metallicity of the Heusler crystal lattice requires the atomic lattice sites to be arranged as an L2₁ crystal structure.

The thin film investigations of these materials have been conducted primarily using the deposition techniques of low-temperature sputtering and molecular beam epitaxy (MBE). The deposition conditions of these methods commonly required the use of post-growth annealing above 500 K to improve the crystallinity of the thin films in order to achieve both a high degree of long-range crystal order, and the desired arrangement of the atomic lattice sites.

This thesis investigates the growth of as-deposited single-crystal Heusler films using the method of pulsed laser deposition (PLD). This technique is ideal for exploring hetero-epitaxial deposition of complex materials, like the ternary Heusler alloys, by utilising the vaporisation of stoichiometric targets.

The deposition conditions that result in single-crystal thin films can be efficiently investigated by altering the growth parameters of the laser fluence, the laser repetition rate, the substrate material, and the substrate temperature.

Thin films of the Heusler alloys, Co₂MnGa and Co₂MnGe, were created using PLD to investigate the growth parameters required to produce single-crystal films that are atomically arranged as the L2₁ crystal structure, with a high degree of long-range crystal order.

The films were measured using the diffraction methods of in-situ RHEED and XRD to examine the properties of the crystal lattices. SEM imaging was used to aid the identification of the films’ growth modes and quantify the particulate densities on the surface of the films.

The magnetic and magnetotransport properties of magnetisation hysteresis, Hall resistivity, and magnetoresistance were investigated by conducting measurements with a SQUID and PPMS in fields up to 5 T, with applied temperatures of 3 – 300 K.

Single-crystal Co₂MnGa thin films were successfully deposited using PLD on the substrates of MgO(100) and GaAs(100) heated to temperatures of 450 - 700°C. The Co₂MnGa thin films that exhibited structural and magnetic properties in agreement with bulk Co₂MnGa were produced using the optimised substrate temperature of 450°C.

The minimum atomic disorder of the Co₂MnGa film series was identified from XRD measurements of the (100) crystal planes as the B2 phase. The L2₁ phase was confirmed for Co₂MnGa deposited at 700°C on MgO(100) from XRD measurements of the superlattice crystal planes.