Orthogonal magnetic impurity in antiferromagnet YFeO3 single crystal: magnetic resonance and magnetisation measurements

Quasioptical study of antiferromagnetic resonance in YFeO3 at submillimeter wavelength under high pulsed magnetic fields

“…We note the marked resonance signal despite the low impurity concentration (c imp $ 3.5 Â 10 À4 according to Ref. [14]). At temperatures above 40 K the intensity of the impurity resonance modes is significantly reduced due to a change of energy level population of the Fe 3+ ions in c-positions.…”

“…4 can be identified as impurity modes. The descending branch m À i ðHÞði ¼ 1; 2; 3; 4; 5Þ including a group of five lines represents the known impurity modes observed in work [14], while the ascending frequencies m þ i ðHÞ is a new impurity branch consisting of also five lines. In the transmission spectra measured without analyzer, the impurity modes look like usual absorption lines while for the crossed analyzer and polarizer geometry the lineshape of the modes changes qualitatively and reveals marked ''positive" and ''negative" peaks ( bling the derivative of the absorption lines.…”

“…Similar spin-Hamiltonian (in a simpler form) was used in Ref. [14] to describe the descending branch of the impurity modes.…”

“…Besides two AFMR modes (quasiferromagnetic and quasiantiferromagnetic modes, respectively, at m 1 $ 300 GHz and m 2 $ 590 GHz for 4.2 K [5,8,9]), YFeO 3 exhibits at low temperatures (T < 50 K) also few impurities modes m imp at 255-300 GHz at zero magnetic field [13,9]. Magnetic field applied along the c-axis results in softening of the impurity modes, which were assigned to magneto-dipolar transitions in 6 S 5/2 multiplet of Fe 3+ ''impurity" ions in c-sites [14]. Such behavior of the impurity modes, representing actually electron paramagnetic resonance in internal exchange and external magnetic fields, could be explained by an opposite direction of the internal effective field and the external one which determines a descending impurity branch for fields below the threshold field H 0 $ 15 T [14] and suggests the existence of an ascending impurity branch for H > H 0 .…”

“…Magnetic field applied along the c-axis results in softening of the impurity modes, which were assigned to magneto-dipolar transitions in 6 S 5/2 multiplet of Fe 3+ ''impurity" ions in c-sites [14]. Such behavior of the impurity modes, representing actually electron paramagnetic resonance in internal exchange and external magnetic fields, could be explained by an opposite direction of the internal effective field and the external one which determines a descending impurity branch for fields below the threshold field H 0 $ 15 T [14] and suggests the existence of an ascending impurity branch for H > H 0 . The search for such high-field impurity brunch was one of the aims of this work.…”