By Joseph Woelfel, TheStreet.com

Barclays (BCS) CEO Bob Diamond has resigned, the second official to step down at the bank in the wake of an alleged interest-rate rigging scandal. Chairman Marcus Agius will lead the search for Diamond's replacement. Agius resigned Monday following the bank's $453 million settlement of an investigation into alleged interest rate manipulation. Agius will step down once a new chairman has been chosen, a spokesperson at the bank said Tuesday.

Regulators in the U.S. and the U.K. alleged that Barclays had submitted false data for setting the London interbank offered rate, or Libor, between 2005 and 2009. "The external pressure placed on Barclays has reached a level that risks damaging the franchise -- I cannot let that happen," Diamond said in a statement Tuesday. The Wall Street Journal, citing sources, reported Tuesday that Barclays Chief Operating Officer Jerry del Missier also is likely to step down.

Microsoft (MSFT) announced plans Monday to record an asset impairment charge of $6.2 billion on its acquisition of aQuantive. Microsoft's 2007 deal for aQuantive was valued at $6.3 billion. The charge is to be recorded in the company's results for the fiscal fourth quarter that ended in June.

The U.S. Justice Department is investigating Chesapeake Energy (CHK) and Encana (ECA) for possible collusion in connection with Michigan land deals, a source close to the probe told Reuters. A Reuters report uncovered emails showing the two natural gas companies in 2010 discussed how to avoid bidding against each other in a public land auction in Michigan and in nine prospective deals with private land owners in the state.

Carmakers, including General Motors (GM) and Ford (F), are expected Tuesday to post U.S. sales results for June.