Magnetic phase diagram of Sr2−xLaxIrO4 synth

Abstract

We report the crystal structure and physical properties of Sr 2−x La x IrO 4 synthesized by mechanical alloying. The magnetic transition temperature T N and electrical resistivity decreased with increasing La doping, consistent with previous studies involving single-crystalline samples. We also identified the relationship between T N and tetragonal distortion (c/a) in this system. This result suggests that the magnetism of the Sr214 system is strongly correlated with its crystal structure. Zero-field muon spin rotation/relaxation studies revealed that short-range antiferromagnetic ordering is realized in Sr 1.9 La 0.1 IrO 4 ; also, the spin-glass state is stabilized in the low-temperature region. The Ir moment estimated from the longitudinal field μSR results is 0.045 μ B , ten times smaller than that of Sr 2 IrO 4 (∼0.4 μ B), indicating that electrons are introduced into the Ir atoms.

μSR Study of the Magnetic State in Hole and Electron Doped Sr2IrO4

“…On the other hand, the effective Ir moment size of Sr 2−x La x IrO 4 |μ Ir | was determined as 0.053 (x = 0.05) μ B . This value is about eight times smaller than that of Sr 2 IrO 4 and consistent with the previous magnetic susceptibility measurements [4]. Thus, the decrease of the Ir moment is attributed to the effects of electron doping by La substitution.…”

“…At temperatures below 50 K, the spectral damping becomes faster with decreasing temperature and the spectrum at 3 K shows a shallow dip structure. This result is similar to that for x = 0.1 [4] and likely originates from the spin-glass state at low temperatures. To understand the magnetism of this system, we fitted the ZF-time spectra using the following function:…”

“…A gradual decrease of β from 1 to 0.6 appears at approximately 190 K, corresponding to T N . Then, β remains approximately 0.6 from 190 K to 50 K. This value of β is likely associated with a short-range magnetic Griffiths phase reported in previous μSR measurements [4]. As the temperature is lowered further (below 50 K), β reaches approximately 1/3-a typical value in dilute spin-glass systems [7,8].…”

“…1d shows the LF-μSR spectra of the x = 0.05 sample measured at T = 3 K. The LF-μSR spectra display a systematic upward shift with increasing field. On the basis of our previous μSR study [4], the static width of the local fields at the muon sites ∆ was estimated to be 5.30 μs −1 . Thus, the characteristic field at a muon site was determined as ∆/γ μ = 62.2 G. In Sr 2 IrO 4 , the moment size of the J eff = 1/2 pseudospin is reduced to 0.4 μ B , as confirmed by previous μSR, RIXS, and neutron diffraction measurements [6,9,10].…”

“…Recently, our group have investigated the substitution eff ect for Sr 2 IrO 4 to confirm the influence of band filling control of the Mott insulating state. We synthesized a hole doping sample of Sr 2−x K x IrO 4 and an electron doping sample of Sr 2−x La x IrO 4 [3,4]. From the magnetic susceptibility data, the absolute magnetic moment, and Néel temperature, T N , of Sr 2−x La x IrO 4 decrease with increasing La doping.…”