Magnetic domain structure on the surface of the layer-structured ferromagnet La1.4Sr1.6Mn2O7 was observed in the temperature range from 37 to 97 kelvin with a scanning Hall probe microscope. The sensitivity to temperature of the domain structure changes was large relative to that in conventional ferromagnets. The stable and spontaneous appearance of magnetic bubble domains without an external magnetic field was observed in the neighborhood of 70 kelvin. The phenomenon observed could provide a potential route toward magnetic bubble memory.