Spin-phonon coupling in epitaxialSr0.6Ba0.4MnO3thin films

Abstract

Spin-phonon coupling is investigated in epitaxially strained Sr 1−x Ba x MnO 3 thin films with perovskite structure by means of microwave (MW) and infrared (IR) spectroscopy. In this work we focus on the Sr 0.6 Ba 0.4 MnO 3 composition grown on (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 substrate. The MW complex electromagnetic response shows a decrease in the real part and a clear anomaly in the imaginary part around 150 K. Moreover, it coincides with a 17% hardening of the lowest-frequency polar phonon seen in IR reflectance spectra. In order to further elucidate this phenomenon, low-energy muon-spin spectroscopy was carried out, signaling the emergence of antiferromagnetic order with Néel temperature (T N ) around 150 K. Thus, our results confirm that epitaxial Sr 0.6 Ba 0.4 MnO 3 thin films display strong spin-phonon coupling below T N , which may stimulate further research on tuning the magnetoelectric coupling by controlling the epitaxial strain and chemical pressure in the Sr 1−x Ba x MnO 3 system.

Dielectric relaxation in epitaxial films of paraelectric-magnetic SrTiO3-SrMnO3 solid solution

“…Magnetic-dielectric coupling is manifested by similar temperatures of the dielectric anomalies and magnetic ordering and ascribed to strong spin-phonon correlations in these materials. [6][7][8][9][10][11][12]20,25,26 Concurrently, a magnetic-field-dependent electrical conduction of undescribed origin was also shown to produce typical magneto-dielectric response. 27 We note that (Sr,Ba)MnO 3 , (Sr,Ca)MnO 3 , and Sr(Mn,Ti)O 3 systems exhibit profound conductivity, the mechanism of which is under debate.…”

“…1(b), 1(c), and 1(e)] is remarkably similar to that in thin epitaxial Sr 0.6 Ba 0.4 MnO 3 films. 20 The anomalies were considered as a proof for spin-phonon coupling in those films. 20 However, the lack of conductivity data makes this interpretation incomplete, because electron-phonon coupling may give the same apparent electrical behavior.…”

Relaxation Mechanisms and Strain-Controlled Oxygen Vacancies in Epitaxial SrMnO3 Films

“…Some experimental confirmations of these first-principles predictions came in recent years: incipient ferroelectricity was shown in epitaxially strained CaMnO 3 films, ferroelectricity was measured at low temperature in (Sr,Ba)­MnO 3 crystals under Ba-induced chemical pressure, and the interplay between magnetic and electrical properties was shown in (Sr,Ba)­MnO 3 films with several compositions. − Yet, the stability of the perovskite phase for increasingly Ba-rich (Sr,Ba)­MnO 3 compounds rapidly deteriorated, preventing the multiferroic character from being attained. Regarding pure epitaxial SrMnO 3 , the initial predictions were partially corroborated by optical second-harmonic generation (SHG) measurements, proving the emergence of a polar state at 300 K in SrMnO 3 films grown under 1.7% tensile epitaxial strain and ferroelectricity at 4 K in strongly strained (3.8%) films .…”