Zhang, Z. H.Z. H.ZhangPinfield, D. J.D. J.PinfieldGálvez-Ortiz, M. C.M. C.Gálvez-OrtizBurningham, B.B.BurninghamLodieu, N.N.LodieuMarocco, F.F.MaroccoBurgasser, A. J.A. J.BurgasserDay-Jones, A. C.A. C.Day-JonesAllard, F.F.AllardJones, H. R. A.H. R. A.JonesHomeier, D.D.HomeierGomes, J.J.GomesSMART, Richard LaurenceRichard LaurenceSMART2021-01-112021-01-1120170035-8711http://hdl.handle.net/20.500.12386/29664We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or near-infrared wavelengths. We also present new optical spectra of three previously known L subdwarfs (WISEA J001450.17-083823.4, 2MASS J00412179+3547133, and ULAS J124425.75+102439.3). We examined the spectral type and metallicity classification of subclasses of known L subdwarfs. We summarized the spectroscopic properties of L subdwarfs with different spectral types and subclasses. We classify these new L subdwarfs by comparing their spectra to known L subdwarfs and L dwarf standards. We estimate temperatures and metallicities of 22 late-type M and L subdwarfs by comparing their spectra to BT-Settl models. We find that L subdwarfs have temperatures between 1500 and 2700 K, which are higher than similar-typed L dwarfs by around 100-400 K depending on different subclasses and subtypes. We constrained the metallicity ranges of subclasses of M, L, and T subdwarfs. We also discussed the spectral-type and absolute magnitude relationships for L and T subdwarfs.STAMPAenPrimeval very low-mass stars and brown dwarfs - I. Six new L subdwarfs, classification and atmospheric propertiesArticle10.1093/mnras/stw24382-s2.0-85017249733000393647600043https://academic.oup.com/mnras/article/464/3/3040/24547802017MNRAS.464.3040ZFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems