Charge/orbital ordering vs. Jahn-Teller distortion in La0.5Sr1.5MnO4

Temperature dependences of a magnetic and an orbital Bragg reflection at the Mn L2,3 edges of La0.5Sr1.5MnO4 have been collected. The temperature evolution of the orbital reflection depends strongly on the X-ray energy and reflects the different order parameters, which are assigned to orbitals and Jahn-Teller distortions. The Jahn-Teller order parameter saturates at 150 K, whereas the orbital order parameter gradually increases. These results are discussed in context with the possible driving forces, the orbital-orbital super exchange and the Jahn-Teller strain field interaction.