Study of the e_g Orbitals in the Bilayer Manganite La_2-2xSr_1+2xMn₂O₇ by Using Magnetic Compton-Profile Measurement

From the magnetic Compton-profile (MCP) measurement, we have directly differentiated for the first time the populations in two e_g-type orbitals ( x²-y² and 3z²-r²) in a manganite. The experimental MCP’s along the [001] direction for La_2-2xSr_1+2xMn₂O₇ at x = 0.35 and 0.42 are fitted by the theoretical profiles obtained from the (MnO₆)^8- ab initio calculations. The calculation confirms that the MCP clearly detects the oxygen hybridization in the e_g orbitals. The e_g state is dominated by the x²-y²-type orbital with almost constant population, while the population in the 3z²-r²-type orbital decreases with increasing the hole concentration x.