Spin-order dependent anomalous Hall effect and magneto-optical effect in the noncollinear antiferromagnets Mn3XN with X=Ga , Zn, Ag, or Ni

Abstract

The anomalous Hall effect (AHE) and the magneto-optical effect (MOE) are two prominent manifestations of time-reversal symmetry breaking in magnetic materials. Noncollinear antiferromagnets (AFMs) have recently attracted a lot of attention owing to the potential emergence of exotic spin orders on geometrically frustrated lattices, which can be characterized by corresponding spin chiralities. By performing first-principles density functional calculations together with group-theory analysis and tight-binding modelling, here we systematically study the spin-order dependent AHE and MOE in representative noncollinear AFMs Mn3XN (X = Ga, Zn, Ag, and Ni). The symmetry-related tensor shape of the intrinsic anomalous Hall conductivity (IAHC) for different spin orders is determined by analyzing the relevant magnetic point groups. We show that while only the xy component of the IAHC tensor is nonzero for right-handed spin chirality, all other elements − σxy, σyz, and σzx − are nonvanishing for a state with left-handed spin chirality owing to lowering of the symmetry. Our tight-binding arguments reveal that the magnitude of IAHC relies on the details of the band structure and that σxy is periodically modulated as the spin rotates in-plane. The IAHC obtained from first principles is found to be rather large, e.g., it amounts to 359 S/cm in Mn3AgN, which is comparable to other well-known noncollinear AFMs such as Mn3Ir and Mn3Ge. We evaluate also the magnetic anisotropy energy and find that the evolution of spin order is related to the number of valence electrons in the X ion. Interestingly, the left-handed spin chirality could exist in Mn3XN with some particular spin configurations. By extending our analysis to finite frequencies, we calculate the optical isotropy [σxx(ω) ≈ σyy(ω) ≈ σzz(ω)] and the magnetooptical anisotropy [σxy(ω) = σyz(ω) = σzx(ω)] of Mn3XN. Similar to the IAHC, the magneto-optical Kerr and Faraday spectra depend strongly on the spin order. The Kerr rotation angles in Mn3XN are in the range of 0.3 ∼ 0.4 deg, which is large and comparable to other noncollinear AFMs like Mn3Pt and Mn3Sn. Our finding of large AHE and MOE in Mn3XN suggests that these materials present an excellent antiferromagnetic platform for realizing novel spintronics and magneto-optical devices. We argue that the spin-order dependent AHE and MOE are indispensable in detecting complex spin structures in noncollinear AFMs. arXiv:1903.11038v1 [cond-mat.mtrl-sci]

Topology analysis for anomalous Hall effect in the noncollinear antiferromagnetic states of Mn3AN (A=Ni, Cu,Huyen1, Suzuki2, Yamauchi3 et al. 2019Phys. Rev. B644302View full textAdd to dashboardCite

“…In this context, anti-perovskite manganese nitrides can be regarded as a new playground to explore the AH effect, since Mn 3 AN (A= Ni, Sn) have been found to show non-collinear AFM in the triangular Mn lattice corresponding to irreducible representations T 1g (Γ + 4 ) and T 2g (Γ + 5 ), respectively [13][14][15] and there are many analogues with the replaced nonmagnetic elements. A recent study on the spin-order dependent AH effect in the non-collinear AFM Mn 3 AN (A= Ga, Zn, Ag, or Ni) also suggested that these compounds are an excellent AFM platform for realizing novel spintronics applications 16 .…”

Spin-torque switching of noncollinear antiferromagnetic antiperovskites

“…Recently, the AHE has been predicted theoretically and confirmed experimentally in Mn based antiperovskite nitrides with the Γ 4g AFM order [29,[57][58][59][60]. Due to the AHC being odd with respect to the time reversal symmetry operation, reversal of the AFM order in the Γ 4g type antiperovskites is expected to change sign of the AHE (Fig.…”

“…In this regard, noncollinear AFM materials [ 22 ] could provide a viable alternative to their collinear counterparts. Recent studies have shown that a number of high temperature noncollinear antiferromagnets, such as Mn 3 X (X = Ga, Ge, Sn or Ir) [ 23 -28 ] and antiperovskite ANMn 3 (A = Ga, Zn, Ag or Ni) [29][30][31] exhibit large anomalous Hall conductivities (AHC). Due to the AHC being odd with respect to time reversal symmetry, reversal of the Néel vectors [ 32 ] in these compounds is expected to change sign of the AHE that can be used as an efficient detection scheme of the AFM order using the standard Hall measurements.…”

“…Recently, it was found that the 𝑇𝑇 � 𝑂𝑂 � symmetry in antiferromagnets can be broken by the noncollinear magnetic order [ 18 ] or non-centrosymmetric arrangement of nonmagnetic atoms [ 19 ]. The broken 𝑇𝑇 � 𝑂𝑂 � symmetry was shown to result in interesting electronic, magnetic and transport properties that previously were only known for ferromagnets, such as the anomalous Hall effect [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], the non-relativistic Zeeman-like band splitting [35][36][37], and the unconventional charge-to-spin conversion [38][39][40][41][42]. The emergence of electric currents with sizable spin polarization is particularly exciting, due to the possible use of these currents and the antiferromagnets generating them in spintronic devices [43][44][45].…”

Nonlinear Anomalous Hall Effect for Néel Vector Detection

“…Recently, the AHE has been discovered in non-collinear antiferromagnets (Fig. 1(a)), such as Mn3X (X = Ga, Ge, Sn, or Ir) [23,24,25,26,27,28] and Mn3AN (A = Ga, Zn, Ag, or Ni) [29,30,31], and collinear antiferromagnets with specific arrangement of nonmagnetic atoms in the crystal lattice (Fig. 1(b)), such as CoNb3S6 [32,33,34].…”