Since physics research is an activity of an active international community, international visits are a common way for physicists to share scientific knowledge and skills. International mobility of physicists is also important for PhD physics study and research training. We investigated personal and social factors that influenced the decision for international PhD students to study physics in Australia. Eleven international PhD physics students at a university in Australia participated in individual in-depth interviews. As a result, multidimensional factors on their decision to engage in PhD study abroad were found. Although highly regarded research fields and/or experts in fields appeared as a strong influential factor, other personal and social contexts also influence the final decision. This indicates intertwined aspects of personal learning desire and social contexts for PhD international learners in physics who are underrepresented in the higher education literature.