Magneto-optical properties of ferromagnetic chromium trihalides

Dillon, J. F.; Kamimura, Hiroshi; Remeika, J. P.

doi:10.1016/0022-3697(66)90148-x

Cited by 120 publications

(106 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The CrI 3 data are from the sample in Supplementary Fig. 4, while the data for CrBr 3 and CrCl 3 are compiled from refs 13,[19][20][21][22] . c, Configurational coordinate diagram in the harmonic approximation for the observed ligand-field 4 T 2 absorption and PL.…”

Section: Methodsmentioning

confidence: 99%

“…1 ) in the 1990s 12 . Central to progress in these fields, optical experiments have led to a deep understanding of electronic structure, magnetization dynamics and interactions between magnetism and light 8,[13][14][15] . While the fascinating physics in the quantum structures of diluted magnetic semiconductors has propelled spintronics research over the last few decades 16 , there has been a comparative lack of non-metallic nanoscale materials hosting intrinsic magnetism.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Ligand-field helical luminescence in a 2D ferromagnetic insulator

et al. 2017

View full text Add to dashboard Cite

Bulk chromium tri-iodide (CrI 3 ) has long been known as a layered van der Waals ferromagnet 1 . However, its monolayer form was only recently isolated and confirmed to be a truly two-dimensional (2D) ferromagnet 2 , providing a new platform for investigating light-matter interactions and magnetooptical phenomena in the atomically thin limit. Here, we report spontaneous circularly polarized photoluminescence in monolayer CrI 3 under linearly polarized excitation, with heli city determined by the monolayer magnetization direction. In contrast, the bilayer CrI 3 photoluminescence exhibits vanishing circular polarization, supporting the recently uncovered anomalous antiferromagnetic interlayer coupling in CrI 3 bilayers 2 . Distinct from the Wannier-Mott excitons that dominate the optical response in well-known 2D van der Waals semiconductors 3 , our absorption and layer-dependent photoluminescence measurements reveal the importance of ligandfield and charge-transfer transitions to the optoelectronic response of atomically thin CrI 3 . We attribute the photoluminescence to a parity-forbidden d-d transition characteristic of Cr 3+ complexes, which displays broad linewidth due to strong vibronic coupling and thickness-independent peak energy due to its localized molecular orbital nature.Van der Waals layered materials offer fascinating opportunities for studying light-matter interactions in the 2D limit. For instance, monolayer semiconducting transition metal dichalcogenides (for example, WSe 2 ) enable coupling between the helicity of light and the valley degree of freedom 4 . In all non-metallic 2D materials to date, it has been established that tightly bound Wannier-Mott excitons dominate the intrinsic optical response 3 , and there has been rapid progress in studying 2D excitonic interactions, dynamics and spin/valley physics 3,5 . However, none of these 2D materials possesses long-range magnetic order. A monolayer semiconductor or insulator with intrinsic magnetism would enable the study of novel photo-physical phenomena and the interplay with underlying magnetic order, possibly involving physics incompatible with the Wannier-Mott excitonic picture.On the other hand, the exploration of ferromagnetism in non-metallic bulk materials has a long history. Early studies examined the intrinsic ferromagnetic ordering of a variety of insulating and semiconducting materials, including, for example, the ferrites and ferrospinels 6 , Cr trihalides 7 , Eu chalcogenides 8 and Cr spinels 9 . Later, with the introduction of magnetic dopants into non-magnetic II-VI and III-V semiconductors, diluted magnetic semiconductors captured widespread attention 10 , boosted by the discovery of ferromagnetism in Mn-doped InAs (ref.11 ) and GaAs (ref.1 ) in the 1990s 12 . Central to progress in these fields, optical experiments have led to a deep understanding of electronic structure, magnetization dynamics and interactions between magnetism and light 8,[13][14][15] . While the fascinating physics in the quantum structures of diluted magnet...

show abstract

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Ligand-field helical luminescence in a 2D ferromagnetic insulator

et al. 2017

View full text Add to dashboard Cite

show abstract

“…It shows layered Ising ferromagnetism below a Curie temperature (Tc) of 61 K with an out-of-plane easy-axis (Figs. 1a&b) 29,30 . Given its van der Waals nature, we expect magnetocrystalline anisotropy, which can lift the Mermin-Wagner restriction, to stabilize long-range ferromagnetic ordering even in a monolayer.…”

Section: Main Textmentioning

confidence: 99%

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Huang

Clark

Navarro‐Moratalla

et al. 2017

Nature

4,602

179

4,153

View full text Add to dashboard Cite

Since the celebrated discovery of graphene 1,2 , the family of two-dimensional (2D) materials has grown to encompass a broad range of electronic properties. Recent additions include spin-valley coupled semiconductors 3 , Ising superconductors 4-6 that can be tuned into a quantum metal 7 , possible Mott insulators with tunable charge-density waves 8 , and topological semi-metals with edge transport 9,10 . Despite this progress, there is still no 2D crystal with intrinsic magnetism [11][12][13][14][15][16] , which would be useful for many technologies such as sensing, information, and data storage 17 . Theoretically, magnetic order is prohibited in the 2D isotropic Heisenberg model at finite temperatures by the Mermin-Wagner theorem 18 . However, magnetic anisotropy removes this restriction and enables, for instance, the occurrence of 2D Ising ferromagnetism. Here, we use magneto-optical Kerr effect (MOKE) microscopy to demonstrate that monolayer chromium triiodide (CrI3) is an Ising ferromagnet with out-of-plane spin orientation. Its Curie temperature of 45 K is only slightly lower than the 61 K of the bulk crystal, consistent with a weak interlayer coupling. Moreover, our studies suggest a layer-dependent magnetic phase transition, showcasing the hallmark thickness-dependent physical properties typical of van der Waals crystals 19-21 . Remarkably, bilayer CrI3 displays suppressed magnetization with a metamagnetic effect 22 , while in trilayer the interlayer ferromagnetism observed in the bulk crystal is restored. Our work creates opportunities for studying magnetism by harnessing the unique features of atomically-thin materials, such as electrical control for realizing magnetoelectronics 13,23 , and van der Waals engineering for novel interface phenomena 17 . 2 Main Text:Magnetic anisotropy is an important requirement for realizing 2D magnetism. In ultrathin metallic films, an easy-axis can originate from symmetry reduction at the interface/surface, which hinges on substrate properties and interface quality [24][25][26] . In contrast, most van der Waals magnets have an intrinsic magnetocrystalline anisotropy due to the reduced crystal symmetry of their layered structures. This offers the coveted possibility to retain a magnetic ground state in the monolayer limit. In addition to studying magnetism in naturally formed crystals in the true 2D limit, layered magnets provide a platform for studying the thickness dependence of magnetism in isolated single crystals where the interaction with the underlying substrate is weak. Namely, the covalently bonded van der Waals layers prevent complex magnetization reorientations induced by epitaxial lattice reconstruction and strain 23 . For layered materials, these advantages come at a low fabrication cost, since the micromechanical exfoliation technique 27 is much simpler than conventional approaches requiring sputtering or sophisticated molecular beam epitaxy.A variety of layered magnetic compounds have recently drawn increased interest due to the possibility of re...

show abstract

“…Microscopically, Faraday effects are based on electric dipole transitions [23]. From crystal-field theory of chromium trihalides and similar for chromia, it is known that an appreciable Faraday effect originates from the average dipole moment of d-d transitions [21,24]. In chromia, these are the transitions between the ground state 4 A 2 and excited states of 4 T 2 type of the Cr 3þ ions.…”

mentioning

confidence: 99%