Magnetic field induced softening of spin waves and hard-axis order in the Kondo-lattice ferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>CeAgSb</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
Physical review. B./Physical review. B