Mutual induction of magnetic 3dand 4forder in multiferroic hexagonal ErMnO3

Abstract

The complex interplay between the 3d and 4 f moments in hexagonal ErMnO 3 is investigated by magnetization, optical second harmonic generation, and neutron-diffraction measurements. We revise the phase diagram and provide a microscopic model for the emergent spin structures with a special focus on the intermediary phase transitions. Our measurements reveal that the 3d exchange between Mn 3+ ions dominates the magnetic symmetry at 10 K < T < T N with Mn 3+ order according to the Γ 4 representation triggering 4 f ordering according to the same representation on the Er 3+ (4b) site. Below 10 K the magnetic order is governed by 4 f exchange interactions of Er 3+ ions on the 2a site. The magnetic Er 3+ (2a) order according to the representation Γ 2 induces a magnetic reorientation (Γ 4 → Γ 2 ) at the Er 3+ (4b) and the Mn 3+ sites. Our findings highlight the fundamentally different roles the Mn 3+ , R 3+ (2a), and R 3+ (4b) magnetism play in establishing the magnetic phase diagram of the hexagonal RMnO 3 system.

Hexagonal Manganites—(RMnO3): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

“…The anomaly at̃develops at magnetic fields above 7 kOe and moves quickly to higher temperature with increasing field . The field and temperature dependent data of the magnetic susceptibility recently published [186] are in good agreement with our results shown in Figure 34.…”

“…At higher magnetic fields, a second steep increase of ( ) signals a second phase transition (see Figure 34(a)). The critical field of this transition increases quickly with temperature and is already above the maximum field of 50 kOe at about 14 K. Note the curves of ( ) shown in Figure 34(a) include data collected with increasing as well as decreasing field and no magnetic hysteresis is observed, unlike in the previous publication by Sugie et al The absence of any hysteretic behavior upon increasing or decreasing temperature or field was also confirmed in a recent study of the magnetization of ErMnO 3 to temperatures as low as 80 mK [186]. Furthermore, the first transition at fields below 1000 Oe (inset of Figure 34(a)) was not reported in [105].…”

Magneto- to Electroactive Transmutation of Spin Waves inErMnO3

“…Below T N , the 4b magnetic moments are orientated antiferromagnetically along the c-axis, polarized in the molecular field of the Mn magnetic moments [21] (See Fig.1). Below T' N ≈ 10 K, the 2a magnetic moments order ferromagnetically along the c-axis and produce a spin reorientation at the 4b rare-earth and Mn sites around 5 and 2 K respectively (Γ 2 irreducible representation [18,19]). Besides its multiferroic properties, ErMnO 3 is particularly interesting because of the strong interplay between the Mn 3+ (3d 4 ) magnetism and the Er 3+ (4f 11 ) spins [18,19].…”

“…Below T' N ≈ 10 K, the 2a magnetic moments order ferromagnetically along the c-axis and produce a spin reorientation at the 4b rare-earth and Mn sites around 5 and 2 K respectively (Γ 2 irreducible representation [18,19]). Besides its multiferroic properties, ErMnO 3 is particularly interesting because of the strong interplay between the Mn 3+ (3d 4 ) magnetism and the Er 3+ (4f 11 ) spins [18,19]. We probed the dynamical properties of ErMnO 3 by inelastic neutron scattering and THz/FIR spectroscopies.…”

“…ment in the (a, b) plane (k = 0 propagation vector) takes place at T N = 79 K, primarily produced by the Mn 3+ magnetic moments (Γ 4 irreducible representation [18,19]). On the other hand, the Er 3+ ions occupy two distinct Wyckoff sites, 4b and 2a [20].…”