Iridium-containing oxide magnets are interesting because the different interactions controlling their magnetic properties have similar energies associated with them. This leads to a competition between the interactions and a rich variety of ground states. Ba5AlIr2O11 shows the results of this competition in two particular ways - iridium ions have two different oxidation states (4+ and 5+) and the magnetic moment is much smaller than might otherwise be expected. We propose to investigate the magnetic ground state of this new material with muons because they are a particularly effective microscopic probe of iridium-containing magnets, and also look at the details of the magnetic phase transition to gain a greater understanding of the magnetic interactions in this material.